The computer science books in Snell Library can mostly be found in the call number range QA 75 to QA 76.99. This area is located on the fourth floor, to your left as you exit the main stairwell. (The rest of the QA section is mathematics.) There is also a large number of computing-related books in a portion of the engineering collections -- try the call number ranges around TK 5105, also on the fourth floor (but to your right as you exit the main stairwell).
We also have many computing-related books as e-books. Here are some places you can locate them; you can also find them simply by searching in Scholar OneSearch.
There is a movement in the academic world for open access to online textbooks. Here is a site that will point you to a large number of free online textbooks in computer science!