I've also bought the lonely planet guide book. It seems to be very useful, with many local maps where we can track down the location of the hotels we've booked and also the relative distances to the sights we want to see. I checked out the eyewitness travel guide, which contains many colourful pictures and intersting general facts, but not as detailed as the lonely planet in describing the sights.
There seems to be so many sights and so little time. We've got two weeks during the school holidays... can't wait! It'd be so exciting.