I'd like to recommend taking a tour at Angkor Wat with a local private guide - this is the most effective way to explore the temples, and it's not very expensive. You can see much more than traveling alone with a book, while you still have the freedom and can decide where and when you want to go.
I did my Angkor tour with Sowanna Yun, who provided excellent service. He is very reliable and professional guide, and also a very good person. It was a private tour with a custom itinerary. You can see examples of the itineraries on his site (cambodianguide.com), but again traveling with a private guide gives you absolute flexibility.
We are still in contact with Sowanna, sometimes he sends me beautiful pictures from this amazing place. I think it's very important to support *local guides*, and I'm glad to recommend his service to my friends and to the TripAdvisor visitors.
Also don't miss the sunrise - must see!
Feel free to contact me with specific questions.