I just returned from a trip to Italy which included 4 days in Umbria and 8 days in Tuscany. I found the Blue Guides for both regions outstanding. Not surprisingly, both are quite worn (the best sign of a useful guidebook).
What makes this guidebook stand out is the incredible breadth of coverage of all tourist sites in Tuscany, making it quite thick, but not particularly heavy. (The only guide that I have seen that even comes close in terms of coverage is the Michelin Green Guide for Tuscany.) Each chapter represents a tour which covers either a town and its vicinity or a driving circuit. Within each tour, every conceivable tourist destination is identified, including small towns, churches, squares, public buildings, museums, archeological sites, etc. For significant museums and churches, the guide directs you through the works in a logical order. For the most part, individual works/objects are listed but not discussed, but notable works are identified with asterisks. Particularly remarkable works, such as Cathedrals and great fresco cycles, are discussed in more detail.
If you are interested in Italian art, architecture, and ancient history, then this book tells you where to find it in Tuscany, and provides brief descriptions. The guidebook does not teach you the history of art and architecture in Tuscany, nor should it. For this, you will need to do some additional reading.
Fine maps and a brief history are provided for each significant town. Parking advise is provided for most towns, and I strongly suggest you follow this advise. (I learned this the hard way.) Also pay close attention to the opening hours, which are quite accurate. The guide's hotel and restaurant recommendations seem quite good; they overlap significantly with the Michelin Red Guide and Frommers. Unfortunately, no descriptions or prices are provided, so most people will want another guidebook for this use. Some of the site closure information was out of date, but I expect this to be updated with the 2000 edition.