There's a newer book (2011), "The Garbage Collection Handbook: The Art of Automatic Memory Management" by Richard Jones, Antony Hoskins and Eliot Moss. I haven't read the new one, but it seems to cover a lot of the recent activity around Java GC.
The recent followup "The Garbage Collection Handbook: The Art of Automatic Memory Management" is much more up-to-date, but it has a bit less coverage of the more elementary techniques.
Very readable and approachable. I read the entire book, which I almost never do with technical books.