Are there any good, solid cel-shading books on the market?

Cel-shading is the "hello world" of non-photorealistic rendering (that is to say, it's not that complex and nobody would bother to dedicate an entire book to it). The topic is covered in any good NPR book. Plug "nonphotorealistic rendering" into Amazon and you'll get plenty of results.

http://www.gamedev.net/reference/articles/article1438.asp

There wont be a full book on cel-shading, it's just an algorithm and its not very hard to achieve.

Ok... I didn't know it was just a form of rendering. This is wonderful, thank you.

Well, its a form of rendering, but for the best results (what you see in most cel-shaded games), it requires carefully done diffuse textures too. But yeah, other than that, its mostly just a rendering technique.