Over at the other place, I've given some suggestions for books on Aquinas and on some of the philosophical background that it's useful to have when reading Aquinas. You can find these suggestions here, here and here.
Another good place to look is Edward Feser's blog. In particular, he has a series for anyone wanting to build a Scholastic's bookshelf. You can find these posts here, here and here.
A Plug For The Sisters...
2 hours ago