Thomas Aquinas: Recommended Resources
Most material on Aquinas gets very philosophical very quickly. This is unfortunate, as the first sight of a passage like "every essence or quiddity can be understood without knowing anything about its existing (esse)" makes a typical non-philosopher put down the book and pick up the remote. Some authors have realized this, though, and have made noble attempts to put Thomas's ideas on the low shelf. Below are several examples, followed by some weightier matter.
Aquinas 101: Crash courses
Thomas Aquinas in 90 Minutes, by Paul Strathern (Ivan R. Dee, 1998), mixes wisecracks and information in roughly equal proportions, but it does give readers a basic understanding of Aquinas's big ideas. Hooked on Philosophy: Aquinas Made Easy, by Robert O'Donnell (Alba House, 1995), is more enlightening while still very readable.
G.K. Chesterton's famous Saint Thomas Aquinas: "The Dumb Ox" scores high on readability and flair ("The gown that could contain the colossal friar is not kept in stock" is just one memorable phrase) but lacks a bit in coherence. Not quite a biography, but not quite anything else, the book reveals as much about Chesterton and his era as it does about Aquinas. Still, eminent scholar Etienne Gilson called it "the best book ever written on St. Thomas."
A First Glance at St. Thomas Aquinas: A Handbook for Peeping Thomists, by Ralph McInerny, is another beginner's gem—if you can find it (it's out of print).
Aquinas 201: Original sources
Reading Thomas's work can never be classed as "easy," but some versions are friendlier than others. Summa Theologiae: A Concise Translation, edited by Timothy McDermott (Thomas More, 1997), could be considered the "Living Thomas." Peter Kreeft uses an older translation but offers many comprehension ...