From Edward Feser, here is a list of helpful introductory volumes for the study of Thomistic philosophy, especially Neo-scholastic Thomism.

I am familiar with only two of the books listed by Feser, but I particularly like Wallace’s Elements of Philosophy. This is a textbook for the Natural Philosophy class, but it is simply a very good summary of Thomist thought, and it ought to be useful to just about anyone. Adler’s Ten Philosophical Mistakes is interesting, I read that book for a high school class once. It is definitely less technical, and more on a popular level. Probably not as useful for graduate study of philosophy, but interesting in its own right.