What is the best book for SCJP/OCPJP exam preparation?

There are two major books for the exam preparation:


SCJP Sun Certified Programmer for Java 6 Exam 310-065, by Katherine Sierra, Bert Bates


A Programmer's Guide to Java SCJP Certification: A Comprehensive Primer (3rd Edition), by Khalid Mughal, Rolf Rasmussen

I've read both books and must admit that "SCJP Sun Certified Programmer for Java 6 Exam 310-065, by Katherine Sierra" is the best. You can also have a look into

OCP Java SE 6 Programmer Practice Exams (Exam 310-065) (Certification Press), by Bert Bates, Katherine Sierra
I can say it's like a companion book there are a plenty of nice mock exam questions.

I can say that you shouldn't use "A Programmer's Guide to Java SCJP Certification: A Comprehensive Primer (3rd Edition), by Khalid Mughal, Rolf Rasmussen" because:

• there too many unnecessary info which is totally useless on exam
• book written style isn't perfect, it's really hard to follow the main idea
• explanation of some ideas is very complex and bloated, it can be simplified
• book typographic style is really ugly in comparison with "SCJP Sun Certified Programmer for Java 6 Exam 310-065, by Katherine Sierra" 

Your can simplify your exam preparation if you stick to one book. Keep in mind your goal is optimize the exam preparation and avoid the redundant reading.