Reading Non-English books
Although the number of go books in English is fairly limited, there is probably enough reading material available to satisfy study needs until shodan or so. It goes without saying that there is an enormous collection of go-related literature in Korean, Chinese and Japanese. Although I read somewhere that the average quality of that material is not very high and the same material is covered many times over, some of it has the advantages of being either very extensive, like the Japanese tesuji dictionaries I saw in Alain Wettach's hands a couple of years ago, or dirt cheap, like the $2 tsumego paperbacks I bought in China.
Oriental books with a high text-to-diagram ratio are normally only of value to people proficient in the language. (Well, in fact the same point could be made for English.) This is not necessarily the case for tsumego, where you can get most of the understanding out of the diagrams, or game collections if you're not interested in the comments. Basic Japanese for Reading Go Books is a page to help you get started.
For Korean Terms see Korean Go Terms
For Chinese Terms see Chinese Go Terms
When buying or ordering books, it is useful to know the title and/or topic, of course, which is why I want to start a collection of reference material here.
Please feel free to copy ISBN numbers from my linked page below. --RobertJasiek
nachtrabe: I've been putting together a language reference for Korean books with the Japanese, English, and Korean terms. Feedback and corrections are welcome and I hope that people find it useful.