Eyewitness Travel Guides have lots of photos, floor plans, and maps, as well as suggestions about what to see, where to go, and what to do in Rome.
The National Geographic Traveler's book includes photos and detailed maps, mapped walking tours, and visitor information.
This well-written, in-depth book presents 10 different walks through the city with lots of detail about monuments and history. This is a great book for those who want something more than the usual guidebook.
"Quiet Corners of Rome" by David Downie explores 60 peaceful places of beauty in Rome, away from the noise and crowds of the city, each with beautiful photos. The book is small and easy to carry along on your visit to Rome. It's also a great gift book or book for the armchair traveler.
"Rome the Second Time," part of the Curious Traveler Series, has 15 itineraries that don't go to the Colosseum. If you've been to Rome before and want to see something more than the usual tourist sites, this book has detailed suggestions. It's full of interesting tidbits so it's a good read even if you're not doing the walks. It's also available for Kindle.
A follow up to "Rome the Second Time," Modern Rome outlines walks in three different 20th-century Roman neighborhoods and on the staircases of Trastevere. It's also interesting to read even if you're not going to do the walks. The book is available on Kindle, but it can be difficult to read the maps in the basic Kindle format, so if you really want to do the walks you may prefer the paperback version.
Lonely Planet has more than 800 places to go in Rome and 30 maps. There are local tips from residents of Rome and information about history, art, and architecture, as well as where to eat and drink. It's also available on Kindle.
While this book is fiction, it's a good introduction to the rise of early Christianity and the lives of Saints John and Paul. Read the book before you visit the Case Romane archeological site, ancient Roman houses and early Christian site below the Church of Saints John and Paul in Rome. It's also available on Kindle.
Flavors of Rome takes a look at the food of Rome and how it will be different from Italian food in the United States. There are good restaurant recommendations and a handy food glossary at the end. The book is small and lightweight so easy to carry on a trip to Rome.