Obtaining the SCJP Study Guide from Kathy Sierra is the first step in the good direction.
I personally believe it all depends a little bit on your own needs, do you need to obtain the certification quickly because your employer expects you to.
If that's the case then try to go through the study guide and do a few mock exams and write your exam.
However, my preferred way, is that you go through the book you already have and practice a lot, I mean a lot. This is the only way to get some practical experience with the
Java language.
Did I already say you need to practice?
The JLS might help too. After you feel confident take the objectives from the exam and start with mock-exams. See my signature for more information.
No matter what you decide: all the best to you.