Personally, I don't think buying a book is necessary. The key things are:
1. The exam blueprint - to guide you
2. The documentation - to read
3. The software - to play
The items in the exam are all set based on the objectives in the blueprint, validated against the documentation, and so found that some items could only be answered by having had the hands-on experience.
Can you do the exam first? Yes. Have a look at this post on my blog though: http://vmwaretraining.blogspot.co.uk/2012/06/vcp-common-questions.html?m=0