Other than the Smithsonian, tourists come to DC for the architecture. From the historic colonial and Federal buildings in Georgetown to the enormous neo-classical monuments, DC is about buildings. In fact, Washington has one of the most striking collections of public structures in the world.
It's a good thing too, because DC needs a BIG draw. It is not the most hospitable city, to say the least. A convoluted and insufficient system of roads and highways, a skeletal subway system, and an enormously competitive population combine to make DC a high-strung city. It's the road rage capital of the world, so keep this in mind when you visit. Take your time and enjoy the buildings. If the locals don't like it, who cares? This is YOUR city.
Of course, Washington DC is known for immense neo-classicism, designed by the country's (and the world's) most important Beaux-Arts architects. This guide does a nice job of presenting the impressive array of neo-classical structures to the reader. The book is really quite comprehensive. In its fourth edition, the author knows what buildings we're going to be interested in. The essays are well written, for the most part, tending toward architectural detail rather than historical provenance. Editorializing is kept to a minimum, which is nice considering the stark emotions Washington DC is able to inspire. The building selection is good, with a nice balance between historic, neo-classical and modern. I wish the authors had spent a little less time on the neo-classical theme and fleshed out Federal Georgetown more. An excursion to Alexandria would have been nice too. I know, you can't have it all.
Most of the photography is off-the-shelf and is characteristically mundane, though practical. There are about 500 well-chosen entries here, ranging from small colonial houses to the Capitol. The book is organized in typical AIA format, with chapters dedicated to specific neighborhoods. There are good introductory essays which will help the reader understand the enormous conservatism of DC architecture, even in its "modern" buildings. As a planned city from foundation, DC was always supposed to be our Paris. The experiment was partially successful, but the mixture of building stock offered by quaint (and affluent) Georgetown, Adams-Morgan, Foggy Bottom, Cleveland Park and others make Washington, DC a more complex and organic architectural ensemble than visitors usually expect. This book makes DC buildings accessible and real, rather than simply presenting a catalog of cold, pompous piles.
A fifth edition of this book is one the way, which should expand on a book that is already considered the standard. I highly recommend this book for architectural historians and serious cultural tourists.