You can grab a book a day for free from Packt Pub, https://www.packtpub.com/packt/offers/free-learning.

This script allows you to download, not only those books, but all of the books listed in "My Books" within your account.

This was based on ruby 2.2.3 but you can change the .ruby-version file as there's nothing too exciting in here.

You'll need to edit the config.yml to have your email, password to login to packtpub.com and the path where you want the books to download, which, will need to exist already.

bundle install
bundle exec ruby download-packt-books.rb

It's pretty basic so will output to screen. It won't download the book if the file already exists.