Frommer's Portable Guide to Rio de Janeiro is a useful and practical travel book that visitors to Rio will find quite useful.  The book covers such usual topics as dining, accommodations, and transportation as well as festivals and events, cultural and historical information, and helpful contact information such as websites, immigration requirements, and phone numbers.  The book also contains some maps and is small enough to fit in a pocket or purse. 

Another good Rio travel guide is Insight's Pocket Guide to Rio which has most of the same features as the Frommer's guide, but with the addition of more maps and several beautiful photographs.