[artemonster]

If you want to learn about combinators and have some great fun while doing it I just can't recommend enough of this book: "To Mock a Mockingbird" by Raymond Smullyan. Don't sweat it, buy it, I haven't had so much fun in a long time.

[Jtsummers]

Seconding this book. I jumped back to the beginning of his recreational logic books and have been reading through them this year. Lots of fun, and as a programmer there’s an extra (self-induced) challenge to explore programs that can generate, solve, or interpret the systems and problems he sets up.

[a4isms]

Thirding.

[vga805]

Fourthing.

And also his Godelian Puzzle Book, much fun!