General ⇒ What book on LaTeX and TeX to get?

[Spectrum]

I am an intermediate level TeXnician, having worked with LaTeX for a few years now. I started out working from the Not So Short Introduction to LaTeX and now have a good grasp of most of the features it covers. But I crave more. I am looking for a book that gives more in-depth coverage of LaTeX and TeX, how to use the more advanced features and do more naughty programming, customizing and stuff.

What book would you guys recommend I get? I've been looking at The LaTeX Companion, but there is also a bunch of other books to choose between. Can you give me advice?

Thanks
- Spectrum

[playmobil]

I think the LaTeX Companion is the one you should buy.

[otoomet]

Kopka & Daly "A guide to latex" was really useful for me.

Latex companion is mostly about extra packates (it is a companion to the "latex book" after all).