The University Book Center in the Stamp Student Union maintains the official list of books needed for courses. You can look up your textbooks through their Textbooks Department. A local alternative for buying books is the Maryland Book Exchange located across Route 1 from campus. Several on-line booksellers also list new and used textbooks.
» UBC Textbook Search page

Two places in the area offer warehouse overstock new books. Pick up books for classes or build your library for very little money. Second Story Books has a warehouse in Rockville, MD and Daedalus Books has a warehouse in Columbia, MD. You can also try the Washington Post's list of used book stores in the area.