In addition to The Reformation Study Bible already mentioned, here is a Basic Reformed Annotated Reading List, which an eye towards contemporary writings. The classics already mentioned are all great sources, but they can be tough for modern minds to wrap themselves around. The authors of the sources I list here would all point back to sources such as The Westminster Confession of Faith and all those others, but these might be an easier intro to Reformed theology for you:
Putting Amazing Back into Grace: Who Does What in Salvation? By Michael Horton; 1991; Baker Books: This is a good entry-level laymans introduction to Reformed theology. Hortons book is very reader friendly. Horton examines such basic Reformed positions as the 5-points of Calvinism, the effect of the fall upon man, and free will. Horton also explains the Reformed views of baptism and the Lords Supper. One drawback is that Horton does not really examine covenant theology in this book.
What is Reformed Theology? Understanding the Basics by RC Sproul; 1997; Baker Books: This book, as indicated by the title, covers the basics of Reformed theology. Sprouls book is a little more technical than Hortons book, in that Sproul sprinkles Latin theological terms throughout; however, he always explains them and includes a glossary of foreign terms at the back of the book. This is a solid book that sketches covenant theology and the 5-points of Calvinism.
The Doctrines of Grace: Rediscovering the Evangelical Gospel by James Montgomery Boice and Philip Graham Ryken; 2002; Crossway Books: A very reader friendly presentation of the 5-points of Calvinism. The opening chapter is titled Why Evangelicalism Needs Calvinism, and the final two chapters are titled The True Calvinist and Calvinism at Work. I believe that Boice makes a compelling case for the relevance of Calvinism to modern Christianity. If someone were to choose one book on Reformed theology, this would be a good one.
Chosen by God by RC Sproul; 1986; Tyndale: This book deals specifically with the Reformed views of predestination, free will, and foreknowledge, and how they operate in our salvation. This was the book that convinced me that Reformed theology actually handles the scriptures more accurately than any other viewpoint I have encountered in Christianity.
Willing to Believe: The Controversy Over Free Will by RC Sproul; 1997; Baker Books: A detailed look at the views of free will over the centuries of Christianity. Sproul covers the views of Pelagius, Augustine, Semi-Pelagians, Martin Luther, John Calvin, James Arminius, Jonathan Edwards, Charles Finney, and Lewis Sperry Chafer. If you are a Christian, you will find your position on free will described in this book, and compared to all of the other views.
God of Promise: Introducing Covenant Theology by Michael Horton; 2006; Baker Books: This book is an excellent primer on covenant theology. What is covenant theology? It is an opposing view to the omnipresent dispensational view. Dispensationalism breaks human history down into seven different time periods in which God worked using different methods with different peoples, and is largely responsible for the prevalent end-times view of premillenial, pre-tribulation rapture. Covenant theology interprets scripture to say that God basically only works in two ways
the covenant of works and the covenant of grace.
Debating Calvinism: Five points, Two Views by Dave Hunt and James White; 2004; Multnomah Publishers: From the back cover: Calvinism has been a topic of intense discussion for centuries. In this lively debate, two passionate thinkers take opposing sides, providing valuable responses to the most frequently asked questions about Calvinism. Hunt actually verbalizes many of the objections raised by those reading the above books. It is useful to read Whites responses to those objections.