Since you've already passed SCWCD, I am assuming that you have a good background in
Java. J2ME is essentially a set of Java libraries that
you should not have much of a trouble picking up. Of course, there are nuances specific to installing and deploying applications on a constrained device, which is what the book focuses on. While the main aim of the book is to give the user details about the various sections in the SCMAD exam, it does provide enough background information for someone new to J2ME to get started and does not assume any prior knowledge of mobile programming (other than knowledge of Java language, of course).
So, you should be able to use this book to get a good grasp of J2ME and eventually appear for the exam. As always, I'd recommend that you go to your nearest bookstore where the book is available and take a quick look.