There is a new bundle of interest to game developers, the Game Design and Programming by Pearson Humble Bundle. This bundle contains a large collection of game development books, including several rarer books about game design, all in PDF format.
As with most Humble Bundles, this one is organized into tiers:
1$ Tier
Game Programming in C++
Introduction to Game Systems Design
Mid Tier
Learning Blender
A Game Design Vocabulary
Advanced Game Design
Players Making Descisions
Multiplayer Game Programming
Writing Interactive Music for Video Games
Augmented Reality, Practical Augmented Reality
Unreal Engine VR Cookbook
25$ Tier
Roblox Game Development in 24 Hours
Introduction to Game Design, Prototyping and Development
Fundamentals of Game Design
Unity Game Development in 24 Hours
Games, Design and Play
Game Programming Algorithms and Techniques
[digital]Visual Effects and Compositing
3D User Interfaces
Agile Game Development
As with all Humble Bundles you decide how your money is allocated between Humble, charity, the publisher and if you so choose (and thank you so much if you do!) to help support GFS using this link. You can learn more about the Game Design and Programming bundle in the video below.