Can you recommend some very good reference material from the exam point of view? Will the PMBOK guide third edition alone will help?
While preparing for the PMP examination, referring to 'Guide to PMBOK ' alone will not help and at the same time, there is no other authentic material apart from 'Guide to PMBOK' to act as a reference material. End to end understanding of PMBOK is very important and at the same time, there is no need to mug up things as most of the questions are not very direct.
There are several very good books (PMP exam centric) available in the market.
Project management professional -study guide by Kim Heldman, PMP
The project management Question and answer book by Michael W.Newell, PMP and Marina N. Grashina, PMP
PMP Exam Prep By Rita Mulcahy
are some of them. I will suggest you to rely on the 'Guide to project management body of knowledge, third edition' to understand the concepts, and to use any of the above mentioned books, to get a hang of the exam. Once you register as a member at PMBOKdistilled.com you will get access to simulation tests, which will help you to get a feel of how the real test will be. Sound understanding of the concepts as defined in the PMBOK guide as well as some practice in answering sample questions will help you to prepare well for the PMP credential. My sincere advise is to read the PMBOK guide end to end three times and to do the exercises in one of the above books, three times end to end... and that should do the trick!