Proofs of God

[XmenaceP]

I don't know which book would be suitable for you since you didn't mention if you were looking for an advance treatment or a contemporary one. These are my recommendations, respectively.
First, I would highly recommend St. Thomas' own Commentary on Aristotle and his disputed questions for a thorough (and IMO, irrefutable) proofs for the existence of God.
Second, I recommend the book Aquinas' Proofs for God's Existence: St. Thomas Aquinas on: "The Per Accidens Necessarily Implies the Per Se" by Dennis Bonnette (although that book is pretty pricey).
Lastly, I agree with Caillin's recommendations! But I would add to it his new book that will be coming out soon, "Five Proofs of the Existence of God." It is very affordable (IMO a steal!) and I would say an original work since according to Dr. Feser, "In the years since writing Aquinas, I became convinced that there was a need for a book that approaches things differently.  In particular, there was a need for a book that just gets straight to the main thrust of each of the best arguments for God's existence, introducing the relevant background metaphysical notions along the way rather than in a separate prolegomenon, and without getting bogged down in exegetical questions or being limited to discussing what some particular writer of the past had to say.  That's what Five Proofs does."

You can preorder it here https://www.amazon.com/Five-Proofs-Existence-Edward-Feser/dp/1621641333/ref=sr_1_1?ie=UTF8&qid=1497549805&sr=8-1&keywords=five+proofs+for+God. For more information about the book check out the link Gerard posted. Laudetur Jesus Christus!

[Daniel]

Another interesting proof is Pascal's wager. (It doesn't prove that God exists, but what it does prove is that even if God's existence were unknowable then it would still be a good idea to be Catholic.)

I take this back. The idea is interesting, but I was reading his Pensées the other day, and I must say, this particular proof is horrible. For some reason he basically begins it with the premise that it's impossible to know whether or not God exists, even though we most certainly can know even from our natural reasoning alone that God must exist. And then throughout his argument, Pascal uses a lot of ambiguous-sounding language which doesn't come across as particularly Catholic.