Catholic philosopher Edward Feser has published Aquinas: A Beginner’s Guide (link), an introduction to the thought of St Thomas. Here’s a scrape from Amazon’s page:

One of history’s most influential philosophers and theologians, Thomas Aquinas was the father of modern philosophy of religion, and is infamous for his proofs for God’s existence. In this cogent introduction to his work, Edward Feser argues that you cannot fully understand Aquinas’ philosophy without his theology and vice-versa. Covering his thoughts on the soul, natural law, metaphysics, and the interaction of faith and reason, this is an essential introduction to the great thinker.

Feser is a well-known philosopher who vigorously engages contemporary philosophy and science, from an Aristotelian-Thomistic point of view (i.e., supportive of natural philosophy and A-T metaphysics). While at Amazon.com, check out his important The Last Supersition: A Refutation of the New Atheism.

Feser is also an active blogger, writing on an array of topics ranging from philosophy of mind to contemporary politics. More on his book (including the Table of Contents) at his website.