You can't go far wrong with the old standards: Michelin green and Michelin red . The red guide reliably rates almost all the quality hotels and restaurants in the country. If you are on a student budget, though, you'll find that you probably can't afford any of the establishments listed (the cheapest hotels listed in Rome are about $90/night for a double room).
Michelin publishes two green guides for Italy, one covering the whole country and one just for Rome . If you're planning a driving tour, the country guide is invaluable for its suggested itineraries. The rest of the guide is organized alphabetically, which is very efficient if you're passing through a small town and want to know quickly what its most famous sights are.
The Eyewitness Travel Guides, currently available for Rome , Florence , Venice , and Italy overall were the ones that I put in my photo vest when I was actually walking out for a day of sightseeing. These books have dozens of 3D maps that show you the layout of each district described. Because each building is rendered recognizably, these are much easier to follow than the schematic walking tour maps in other guides or the "turn left after three blocks" instructions you get in guides with less lavish art budgets. The Eyewitness guides also include a large section of recommended hotels, restaurants, shops, entertainment venues, and sports plus practical references and a reasonably good set of city maps. [An Italian friend of mine who had laughed at me during previous trips for my devoted attention to the Michelin guide handled the Eyewitness guide to Rome for a few minutes and then said "You are making me a present of this when you leave."]
If you find the Michelin and the Eyewitness guides rather soulless, then you'll appreciate the Cadogan guides written by Dana Facaros and Michael Pauls. Cadogan can help you decide whether or not you're going to like a place in advance: "Florence is a museum city, and if you don't care to look at pictures, you'd do better to just stay on the train." Facaros and Pauls pick out quirkier details than other authors, e.g., "Almost all of the construction work [on the Colosseum], under Vespasian and Titus, was performed by Jewish slaves, brought here for the purpose after the suppression of their revolt." Despite some well-drawn black & white maps, the Cadogan guide often feels hopelessly outgunned by its color-printed cousins from Michelin and Eyewitness. Here are your options:
Whatever you do, avoid the Let's Go guides. You're in a country with 3000 years of history and you're going to learn about it from a college sophomore? I don't think so. The Let's Go guides do have listings of cheap hotels and restaurants, but you could get that yourself by walking into each city's tourist office and asking for a list of the city's crummiest establishments.
My friends who are classics scholars tend to like the English Blue Guide, which are the most erudite and tell you who did each little painting in each corner of each church, but to really get much out of these, you need to dedicate 30 minutes every night to read up on what you're planning to see the next day. Here are some options in Blue Guides:
The Michelin Red Guide and the Eyewitness guides flag hotels that are wheelchair-accessible. The Eyewitness guides flag wheelchair-accessible sites with in-line symbols. In the Michelin Green guide, you'll have to dig around in the opening hours/prices section in the back of the book.