1. Game Programming Patterns
I recently read Game Programming Patterns from Robert Nystrom one of the best books about programming I've ever read.
I read the entire book from beginning to end in one go, I couldn't stop. Normally I use programming books to fall asleep, the design pattern book of the gang of four doesn't make any exception.
The book Game Programming Pattern from Robert Nystrom on the other hand is one of those very rare books which keeps me awake even late in the night. It is crispy, fun and it explains you the design patterns in a fresh and understandable way. It is also helpfull if you are not a game programmer as it explains the design patterns from the gang of four from a different perspective than you know from your daily work.
One of my favorit one is the command pattern with history functionality. Very use full for level construction tools.
2. The Art Of Game Design
This book is an awsome guide with more then a 100 lenses to look at your game. Written by Jesse Schell a professor of entertainment technology for Carnegie Mellon University's Entertainment Technology Center (ETC).
I like the conept of the lenses in this book, it let you look at your game from different angles to assure you have a fun game in the end. The lenses are summarized in orange boxes which makes this book an awsome guide through your process crafting a fun game. It's like having an instructor on tap.