The Eyewitness Guide to Washington, DC starts off with a brief introductory section that includes a history of the city, general information, as well as a summary of the major galleries, museums, and memorials. This section is almost reminiscent of a Frommer's guide as it includes a best of list and a sample itinerary, which are both staples of that guidebook franchise.
Next, the book moves on to a section-by-section examination of the city. There are five geographical areas within the city as well as two more beyond that are broken down here. Each section offers a reasonable amount of information on major attractions. With the maps, photos, and 3-D style cutaway representations of some of the major buildings the Eyewitness Guide is far superior to others when it comes to giving you a sense of the physical reality of Washington. No amount of words can communicate as thoroughly what a place is like compared to these pictures. I found this invaluable in helping me decide which attractions were most important for me to visit in my limited time in the city.
The book also contains a list of hotels and restaurants but this is the weakest part of the guide. There are only the most basic descriptions and information and no ratings are offered at all. Another guide such as Frommer's Washington, D.C. 2007 (Frommer's Complete) or the The Unofficial Guide to Washington, D.C. (Unofficial Guides) will be far more helpful for this aspect of planning your trip.
Overall, I found this guide very useful for deciding what to do while visiting Washington, DC. It is nowhere near as helpful for choosing restaurants and hotels and I recommend buying a second guide to get more information of that kind. No one guide will have everything you need but this one will be a great start.