Not Built in a Day blends astute architectural observation with basic guidebook practicality. The descriptions combine detail and relevant explanation to make the most lay-person feel expert as they dissect the infinite elements in a church, piazza, or palazzo. For anyone who's been to Rome, the inexorable shuttling between sites makes you numb to the city's splendor, but Not Built in a Day constantly re-orients and reminds the reader that every site contains an element of architectural, historical, or civic wonder that makes the non-stop walking completely worthwhile.
The book's walking tours can be strictly followed (I completed tours 1,2, and 7 without any diversions), but once I had a better feel for the city, I picked specific places that I wanted to see and then read the appropriate entry.
Every guidebook should aspire to be Not Built in a Day