I bought  Sun Certified Enterprise Architect for J2EE Study Guide (Exam 310-051) by Paul Allen, Joseph J. Bambara and  Sun Certified Enterprise Architect for J2EE Technology Study Guide by Mark Cade, Simon Roberts, Enterprise JavaBeans (3rd Edition) by Richard Monson-Haefel
 is too detail for every topic. Those questions trap you into unnecessary detail, which is impossible to appear in real exam.  is very good, but not enough for exam, especially EJB part. The questions are very similar to real exam.  Read Transaction & Life Cycle related chapters carefully. Other chapters are not necessary for part I, but is useful for part II.