I hated property at the beginning of the semester, but now it is my favorite class! My professor has explained to us that he REALLY hated law school, so he wants to make the topic as comprehensive as possible. That being said, these are two supps he recommended to us regarding Real Property (I am using the same casebook as the OP)
Lexis Publishing: A Student's Guide to Estates in Land and Future Interests (Laurence and Minzer), 2d ed. ISBN: 0-8205-2718-1 (This is an EXCELLENT workbook with practice probs you can work through; there are also great charts for quick and easy reference)
Introduction to the Law of Real Property, by Moynihan and Kurtz, 3d ed., ISBN: 0-314-26031-5 (This is a small book, green hardcover, treatise, very easy to understand)
Last but not least, my prof is editor of Powell on Real Property. We get excerpts from him, but you may be able to find the whole thing on Lexis?
If nothing else, get the workbook. It is wondderful!!!!