Game Programming Patterns
I meet a lot of programmers that tell me they got started because they wanted to build games. However, when I ask most of them which games they have built, the list rarely includes anything more than mostly unplayable toy projects.
I can only guess at the reasons for this oddity, but I suspect it might be due to the fact that games are fairly complex. Even if you want to rebuild a fairly simple classic like Space Invaders or Snake you need to know at least a little about event loops, keyboard handling, animation, and collision detection. If your day job involves a different kind of programming, like Web application development, odds are good that you don't get a lot of practice with these concepts.
That may not be your story, but it was definitely mine. This year I decided that it was finally time to learn how to build games. I used several sources to gain this knowledge and some helped more than others, but the biggest win by far was a book called Game Programming Patterns by Bob Nystrom.