The text is Compilers: Principles, Techniques and Tools by Aho, Sethi, and Ullman. There are two editions, the original 1986 edition and a later 2007 edition (with Monica Lam added as a fourth author). You don't necessarily need to buy either book. There will be three copies of the old edition and one of the new available on reserve in the Science library. Most of the new material in the second edition focuses on advanced topics thatwe will not cover in this course.
My suggestion is that you buy a used copy of the old edition. Copies are available from Amazon (starting at $10, including shipping) and elsewhere. The reserve copies are there if you want to use them. While we won't always depend on the book heavily, it should complement the lectures well and is worth buying at a reasonable price. Given the apparent health of the used market and the availability of reserve copies, I haven't ordered copies locally.