A book by Michael Horton on Covenant Theology has just been published. This is an introduction to Covenant Theology. There aren’t a lot of introductory books on Covenant Theology (believe me, I’ve looked), so if you are still confused by how many covenants there (1? 2? 3?) are and would like to understand the differences and similarities between the Old and New Covenant, then you might want to get this book.
I haven’t read it so this is not an endorsement but if you’ve read Putting the Amazing Back Into Grace then you know that he is an excellent writer. And if you haven’t read it go get it because it is a wonderful treatment of Reformed theology.

BTW, it’s cheap, less than you would pay for CD or DVD.