I have written before about the importance of going straight to the sources, especially in regards to theology and biblical studies. Do you want to know about Jonathan Edwards, don’t pick up George Marsden’s magisterial biography of Edwards, pick up Edwards! Go straight to the source. Although I do highly recommend Marsden’s book. Do you want to learn about Augustine, it would seem easier to pick up “Augustine for Armchair Theologians,” but I would recommend you actually start of by reading his Enchiridion. Basically, if you have the option between secondary literature and the primary sources, always go for the primary sources. However, I do understand that reading primary sources can be intimidating. It can be intimidating to picky up the early church fathers, or Church Dogmatics, or Aquinas’ 1600 page tome, the Summa Theologica. But I recommend you do it. At least pick up an abridged version. Currently I’m diving back into Aquinas (its been a long time since we last hung out) by reading Peter Kreeft’s A Shorter Summa, which contains the essential philosophical passages from this masterpiece. Kreeft recognizes that it can be hard to dive into Aquinas, but like C.S. Lewis, Kreeft explains that it is actually easier to read Aquinas than to read books and articles about Aquinas….
There are some excellent books about St. Thomas by the likes of Chestertone, Gilson, Maritain, Pieper, and McInerney, but nothing can substituted for the primary source itself. Secondary source books without St. Thomas always miss something crucial; St. Thomas without them does not.
It is even easier to understand St. Thomas than to understand some books about St. Thomas. Thomas is clearer than Thomists. I have read some fifty or sixty books about St. Thomas, but I never really understood or appreciated him until I read a lot of St. Thomas himself. I find it easier to understand Thomists through Tomas than to understand Thomas through Thomists. The primary source illuminates the secondary sources more than the secondary sources illuminate the primary source.
So go pick up the Summa, its not as hard as it would seem to be. After all Thomas himself said that it was written to “the instruction of beginners.”