Books related to the field of psychology can usually be found in the following call number ranges:
BF1 - BF727 (Psychology)
RC435 - RC571 (Psychiatry & Abnormal Psychology)
Another way to search for books. Google Books offers some full-text books (as PDFs) and excerpts of others. Many of the full-text books are in the public domain, no longer under copyright, and tend to be older.
Google Books is great, but it's not as good as the library! Don't expect miracles!