Hi! Of course, colleges offer intro psych text books, so you might see about getting a college textbook online. They are usually called something like "Introduction to Psychology" or as in your particular interest, "Introduction to Abnormal Psychology." Get the newest one you can, since you would want one that takes into account the new DSM.

(I used to be a college professor.)

Texts do run high, alas. I about fall over when my college-aged son tells me the prices these days.