In French academia, there is one grammar book that rules them all. Initially created as a self-collected series of grammar rules, le bon usage (translates directly as "the good usage," or more correctly as "on correct usage") is THE resource for all questions grammatical in the French language. Maurice Grevisse is the one who did the inital compilation (to use in his own teaching), and although he has passed away (1980), his son-in-law has continuted the tradition of providing updated editions at regular intervals, the last being the 14th edition in 2007.
My French teacher told us about it in class, and although he told us he wouldn't make us buy it, he did insist that if a long-term study of the French language was in our plans (10 years or more), it was simply indespensable for understanding all of the complexities, contradictions, and "exceptions" that exist in French.
So I bought it yesterday. It is 1600 pages, and I had to auction off my virginity to buy it.
No, it wasn't really that expensive, considering that it's an investment in my education. It is quite the massive book, though. So I'll be sending it home with my parents when they come in April. My teacher said it's more complex than anything we would need this semester, but I'd rather get it now and send it home than get home and pay to ship it across the globe. I know how expensive THAT can get, and last time all I ordered was a dictionary on CD-ROM.
So, needless to say, books are some of the things I'll be stocking up on while I'm here and sending home with loved ones.
(Side note: one of the rules that is surely explained in le bon usage is the use of capitalization. In French, many of the things we capitalize in English are simply not capitalized. Ever. Like french and english, or wednesday and january, or east and west. They're all left in lower case. Is it hard for you to read those without wanting to capitalize every one of them? Welcome to my world.)