(I’ve read plenty of others in the past, but this is a 2016/17 reading list.)
- Pro Git – 2nd edition
This first came out in 2009 but was revised in 2014. If you don’t want to build the epub/mobi/PDF yourself, someone has uploaded a recent copy.
- Ansible for Devops Jeff Geerling
- Programmers Guide to Drupal by Jennifer Hodgdon
Make sure you get the 2nd edition which covers Drupal 8.
- Using Drupal 3rd edition
This is the update to cover Drupal 8. As of May 2017 this isn’t complete and the expected publication date has been pushed back to December.