Books are shelved in general subject categories using the Library of Congress classification system. You may want to supplement your use of the catalog with browsing shelf areas for your topic. Below is a brief listing of some of the subject locations in the field of field of psychology.
BF Psychology
RC 321-571 Neurosciences. Biological psychiatry. Neuropsychiatry
RC 435-571 Psychiatry
Sometimes people shy away from books because they are longer to read than a journal article. While this might be technically true, there are some tricks you can use to understand a book's structure and argument, so you DON'T have to read the whole thing.
Once you have a good idea of the book's structure and argument through skimming, you can narrow in on the portions of the text most useful for your research.