My Property professor recommended Peter T. Wendel, A Possessory Estates and Future Interests Primer (2d ed. 2005). It was extremely helpful to me.
I'm going to jump on the Wendel bandwagon. I'm currently using that and I have to say I actually ENJOY possessory estates. That book makes it fun to do. That book dumbs it down for you. The guy repeats things a million times that if you come out not understanding that stuff, then there's something wrong. Seriously get that book. It has practice problems and chart recaps at the end of the chapters. It's sooooooo good.