diff --git a/.fasterer.yml b/.fasterer.yml
new file mode 100644
index 0000000..5ba63b2
--- /dev/null
+++ b/.fasterer.yml
@@ -0,0 +1,21 @@
+speedups:
+  rescue_vs_respond_to: true
+  module_eval: true
+  shuffle_first_vs_sample: true
+  for_loop_vs_each: true
+  each_with_index_vs_while: false
+  map_flatten_vs_flat_map: true
+  reverse_each_vs_reverse_each: true
+  select_first_vs_detect: true
+  sort_vs_sort_by: true
+  fetch_with_argument_vs_block: true
+  keys_each_vs_each_key: true
+  hash_merge_bang_vs_hash_brackets: true
+  block_vs_symbol_to_proc: true
+  proc_call_vs_yield: true
+  gsub_vs_tr: true
+  select_last_vs_reverse_detect: true
+  getter_vs_attr_reader: true
+  setter_vs_attr_writer: true
+
+exclude_paths:
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..59ace56
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+ db.yml
+*.kate-swp
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..41ac85e
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,11 @@
+AllCops:
+  NewCops: enable
+
+Style/RedundantArgument: # (new in 1.4)
+  Enabled: true
+Style/SwapValues: # (new in 1.1)
+  Enabled: true
+Style/FrozenStringLiteralComment:
+  Enabled: false
+Style/Documentation:
+  Enabled: false
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..aedc15b
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.5.3
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..82aa4d4
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,7 @@
+source 'https://rubygems.org'
+
+gem 'awesome_print'
+gem 'faker'
+gem 'fasterer'
+gem 'pry-byebug'
+gem 'rubocop', require: false
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..3ac4b0f
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,58 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.4.1)
+    awesome_print (1.8.0)
+    byebug (11.1.3)
+    coderay (1.1.3)
+    colorize (0.8.1)
+    concurrent-ruby (1.1.7)
+    faker (2.15.1)
+      i18n (>= 1.6, < 2)
+    fasterer (0.8.3)
+      colorize (~> 0.7)
+      ruby_parser (>= 3.14.1)
+    i18n (1.8.5)
+      concurrent-ruby (~> 1.0)
+    method_source (1.0.0)
+    parallel (1.20.1)
+    parser (3.0.0.0)
+      ast (~> 2.4.1)
+    pry (0.13.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    pry-byebug (3.9.0)
+      byebug (~> 11.0)
+      pry (~> 0.13.0)
+    rainbow (3.0.0)
+    regexp_parser (2.0.2)
+    rexml (3.2.4)
+    rubocop (1.7.0)
+      parallel (~> 1.10)
+      parser (>= 2.7.1.5)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml
+      rubocop-ast (>= 1.2.0, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 1.4.0, < 2.0)
+    rubocop-ast (1.3.0)
+      parser (>= 2.7.1.5)
+    ruby-progressbar (1.10.1)
+    ruby_parser (3.15.0)
+      sexp_processor (~> 4.9)
+    sexp_processor (4.15.1)
+    unicode-display_width (1.7.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  awesome_print
+  faker
+  fasterer
+  pry-byebug
+  rubocop
+
+BUNDLED WITH
+   2.0.1
diff --git a/autoload.rb b/autoload.rb
new file mode 100644
index 0000000..1027840
--- /dev/null
+++ b/autoload.rb
@@ -0,0 +1,12 @@
+require 'date'
+require 'yaml'
+require 'faker'
+require_relative 'helpers/error_class'
+require_relative 'helpers/seed'
+require_relative 'modules/validation'
+require_relative 'modules/statistics'
+require_relative 'models/author'
+require_relative 'models/reader'
+require_relative 'models/book'
+require_relative 'models/order'
+require_relative 'models/library'
diff --git a/helpers/error_class.rb b/helpers/error_class.rb
new file mode 100644
index 0000000..2327193
--- /dev/null
+++ b/helpers/error_class.rb
@@ -0,0 +1,14 @@
+class PresenceError < StandardError
+end
+
+class ClassError < StandardError
+end
+
+class EmptinessError < StandardError
+end
+
+class PositiveNumberError < StandardError
+end
+
+class NotAllowedObject < StandardError
+end
diff --git a/helpers/seed.rb b/helpers/seed.rb
new file mode 100644
index 0000000..f5333e7
--- /dev/null
+++ b/helpers/seed.rb
@@ -0,0 +1,46 @@
+class Seed
+  attr_reader :library
+
+  def initialize(library)
+    @library = library
+  end
+
+  def generate_data
+    seed_authors
+    seed_books
+    seed_readers
+    seed_orders
+  end
+
+  def seed_authors
+    10.times do
+      library.add(Author.new(name: Faker::Book.unique.author,
+                     biography: Faker::Lorem.sentence(word_count: 10)))
+    end
+  end
+
+  def seed_books
+    50.times do
+      library.add(Book.new(title: Faker::Book.unique.title,
+                   author: library.authors.sample))
+    end
+  end
+
+  def seed_readers
+    20.times do
+      library.add(Reader.new(name: Faker::Name.unique.name,
+                     email: Faker::Internet.unique.email,
+                     city: Faker::Address.city,
+                     street: Faker::Address.street_name,
+                     house: Faker::Address.building_number.to_i))
+    end
+  end
+
+  def seed_orders
+    100.times do
+      library.add(Order.new(book: library.books.sample,
+                    reader: library.readers.sample,
+                    date: Date.today - rand(0..30)))
+    end
+  end
+end
diff --git a/main.rb b/main.rb
new file mode 100644
index 0000000..a1663df
--- /dev/null
+++ b/main.rb
@@ -0,0 +1,47 @@
+require_relative 'autoload'
+
+reader1 = Reader.new(name: 22, email: '@sabaka', street: '', house: -10)
+reader2 = Reader.new(name: 'Mark', email: 'markus@gmail.com', city: 'London', street: 'Bayker', house: 21)
+author1 = Author.new(name: 'Boris Akunin')
+author2 = Author.new(name: '', biography: 'some bio')
+book1 = Book.new(title: 'BEloe solnce', author: author1)
+book2 = Book.new(title: '', author: 'Djek Vorobey')
+order1 = Order.new(book: book2, reader: reader1)
+order2 = Order.new(book: book1, reader: reader2)
+
+lib = Library.new
+lib.add(reader2)
+lib.add(author1)
+lib.add(book1)
+lib.add(order2)
+
+begin
+  lib.add(author2)
+rescue EmptinessError => e
+  puts e.message
+end
+
+begin
+  lib.add(reader1)
+rescue PresenceError => e
+  puts e.message
+end
+
+begin
+  lib.add(book2)
+rescue ClassError => e
+  puts e.message
+end
+
+begin
+  lib.add(order1)
+rescue ClassError => e
+  puts e.message
+end
+
+Seed.new(lib).generate_data
+lib.store_to_file
+
+puts lib.top_readers(lib.orders)
+puts lib.top_books(lib.orders)
+puts lib.number_readers_of_top_books(lib.orders)
diff --git a/models/author.rb b/models/author.rb
new file mode 100644
index 0000000..63124ed
--- /dev/null
+++ b/models/author.rb
@@ -0,0 +1,33 @@
+class Author
+  include Validator
+
+  attr_reader :name, :biography
+
+  def initialize(name: nil, biography: nil)
+    @name = name
+    @biography = biography
+  end
+
+  def validate!
+    check_presence
+    check_class
+    check_emptiness
+  end
+
+  private
+
+  def check_presence
+    errors = validate_presence :name
+    raise PresenceError, errors unless errors.empty?
+  end
+
+  def check_class
+    errors = validate_class String, :name
+    raise ClassError, errors unless errors.empty?
+  end
+
+  def check_emptiness
+    errors = validate_emptiness :name
+    raise EmptinessError, errors unless errors.empty?
+  end
+end
diff --git a/models/book.rb b/models/book.rb
new file mode 100644
index 0000000..263dbaa
--- /dev/null
+++ b/models/book.rb
@@ -0,0 +1,35 @@
+class Book
+  include Validator
+
+  attr_reader :title, :author
+
+  def initialize(title: nil, author: nil)
+    @title = title
+    @author = author
+  end
+
+  def validate!
+    check_presence
+    check_class
+    check_emptiness
+    @author.validate!
+  end
+
+  private
+
+  def check_presence
+    errors = validate_presence :title, :author
+    raise PresenceError, errors unless errors.empty?
+  end
+
+  def check_class
+    errors = [validate_class(String, :title),
+              validate_class(Author, :author)].flatten
+    raise ClassError, errors unless errors.empty?
+  end
+
+  def check_emptiness
+    errors = validate_emptiness :title
+    raise EmptinessError, errors unless errors.empty?
+  end
+end
diff --git a/models/library.rb b/models/library.rb
new file mode 100644
index 0000000..7e39cb8
--- /dev/null
+++ b/models/library.rb
@@ -0,0 +1,45 @@
+class Library
+  include Statistics
+
+  DATA_FILE = File.expand_path('../db.yml', __dir__)
+  CLASSES = [Integer, String, Date, Author, Book, Library, Order, Reader].freeze
+  ADDING_ERROR = "Object cann't be added to library".freeze
+
+  attr_reader :authors, :books, :readers, :orders
+
+  def initialize
+    @authors = []
+    @books = []
+    @readers = []
+    @orders = []
+
+    load_from_file!
+  end
+
+  def add(entity)
+    entity.validate! if entity.respond_to?(:validate!)
+    case entity
+    when Author then @authors << entity
+    when Book then @books << entity
+    when Reader then @readers << entity
+    when Order then @orders << entity
+    else
+      raise NotAllowedObject, ADDING_ERROR
+    end
+  end
+
+  def load_from_file!
+    data = YAML.safe_load(File.read(DATA_FILE), CLASSES, [], true) if File.exist?(DATA_FILE)
+
+    return unless data
+
+    @authors = data.authors
+    @books = data.books
+    @readers = data.readers
+    @orders = data.orders
+  end
+
+  def store_to_file
+    File.open(DATA_FILE, 'w') { |file| file.write(to_yaml) }
+  end
+end
diff --git a/models/order.rb b/models/order.rb
new file mode 100644
index 0000000..c6d8076
--- /dev/null
+++ b/models/order.rb
@@ -0,0 +1,32 @@
+class Order
+  include Validator
+
+  attr_reader :book, :reader, :date
+
+  def initialize(book: nil, reader: nil, date: Date.today)
+    @book = book
+    @reader = reader
+    @date = date
+  end
+
+  def validate!
+    check_presence
+    check_class
+    @book.validate!
+    @reader.validate!
+  end
+
+  private
+
+  def check_presence
+    errors = validate_presence :book
+    raise PresenceError, errors unless errors.empty?
+  end
+
+  def check_class
+    errors = [validate_class(Book, :book),
+              validate_class(Reader, :reader),
+              validate_class(Date, :date)].flatten
+    raise ClassError, errors unless errors.empty?
+  end
+end
diff --git a/models/reader.rb b/models/reader.rb
new file mode 100644
index 0000000..18aeae4
--- /dev/null
+++ b/models/reader.rb
@@ -0,0 +1,43 @@
+class Reader
+  include Validator
+
+  attr_reader :name, :email, :city, :street, :house
+
+  def initialize(name: nil, email: nil, city: nil, street: nil, house: nil)
+    @name = name
+    @email = email
+    @city = city
+    @street = street
+    @house = house
+  end
+
+  def validate!
+    check_presence
+    check_class
+    check_emptiness
+    check_positive
+  end
+
+  private
+
+  def check_presence
+    errors = validate_presence :name, :email, :city, :street, :house
+    raise PresenceError, errors unless errors.empty?
+  end
+
+  def check_class
+    errors = [validate_class(String, :name, :email, :city, :street),
+              validate_class(Integer, :house)].flatten
+    raise ClassError, errors unless errors.empty?
+  end
+
+  def check_emptiness
+    errors = validate_emptiness :name, :email, :city, :street, :house
+    raise EmptinessError, errors unless errors.empty?
+  end
+
+  def check_positive
+    errors = validate_positive :house
+    raise PositiveNumberError, errors unless errors.empty?
+  end
+end
diff --git a/modules/statistics.rb b/modules/statistics.rb
new file mode 100644
index 0000000..20ab8ea
--- /dev/null
+++ b/modules/statistics.rb
@@ -0,0 +1,17 @@
+module Statistics
+  def top_readers(orders, quantity = 1)
+    top_objects(orders, :reader, quantity).keys.map(&:name)
+  end
+
+  def top_books(orders, quantity = 1)
+    top_objects(orders, :book, quantity).keys.map(&:title)
+  end
+
+  def number_readers_of_top_books(orders, quantity = 1)
+    top_objects(orders, :book, quantity).values.flatten.map(&:reader).uniq.size
+  end
+
+  def top_objects(orders, object, quantity)
+    orders.group_by(&object).max_by(quantity) { |_key, value| value.size }.to_h
+  end
+end
diff --git a/modules/validation.rb b/modules/validation.rb
new file mode 100644
index 0000000..af93e28
--- /dev/null
+++ b/modules/validation.rb
@@ -0,0 +1,29 @@
+module Validator
+  def validate_class(class_name, *attributes)
+    errors = attributes.map do |attr|
+      "Type of #{attr} must be an instance of #{class_name}" if public_send(attr).class != class_name
+    end
+    errors.compact
+  end
+
+  def validate_presence(*attributes)
+    errors = attributes.map do |attr|
+      "#{attr} must be present" if public_send(attr).nil?
+    end
+    errors.compact
+  end
+
+  def validate_emptiness(*attributes)
+    errors = attributes.map do |attr|
+      "#{attr} can't be blank" if public_send(attr) == ''
+    end
+    errors.compact
+  end
+
+  def validate_positive(*attributes)
+    errors = attributes.map do |attr|
+      "#{attr} must be positive" if public_send(attr).to_i <= 0
+    end
+    errors.compact
+  end
+end