I used K&B as my primary study source. Like everybody else says, it's an awesome resource. You really need the book if you want to pass the exam. Make no mistake. This is a difficult exam. You need to know exactly what to study.
I also recommend Dan Chisholm's mock exams. I also had a commercial
test prep which was more similar to the actual exam, but it had quite a few questions on topics that don't appear in the exam, as well as a handful of actual mistakes in the answers. Dan had a lot more questions and I found no mistakes in his answers, although several times I tried hard to prove him wrong. Be ware, Dan is even more cruel and sadistic than the Sun test developers. But if you can get over 50% on his mock exams, you will pass
SCJP easily.
I studied very hard the last five days leading up to the exam. Before that it was off and on for about six months. (You don't want to hear my excuses.) The last six weeks I was pretty good at following the "try for15 minutes" advice from K&B.
Before I went in to take the test I felt I had a pretty good chance of passing, but that was it. By the time I finished the test I was peeved (replace("eev", "iss") that I had missed four questions. I thought I got them all correct. I got over it quickly though, I'm pleased with my results.