I must apologize. I could have sworn that I posted a response to your question. I must have hallucinated it.
I mostly used the typical seminary-style theology manuals in conjunction with the actual sources, but I have heard good things about some of the other works cited here.
I think it's very important, if possible, to approach sacred theology in the same progression with which it is treated at seminary. If you have time, start with a good book on scholastic logic, then move on to philosophy (cosmology, epistemology), and finally to sacred theology. So a brief intro to Aristotle would be helpful. I read Aristotle for Everybody as an undergraduate, going on 40 years ago now, and can't recall if I liked it or not.