To learn the basics I would recommend Mastering Enterprise Java beans by Ed Roman. It is available as a free download For the advanced concepts you could use Enterprise Java beans - Richard Monson Haefel. There is a Head First book available in case you find their style appealing.
My honeysuckle is blooming this year! Now to fertilize this tiny ad:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop