The 'Chroniclers Guide' is indicative of the toolbox approach that White Wolf seem to be taking with a lot of their recent products. Your mileage is going to vary significantly with this title, but the four star rating represents the breadth of uses for the material. Different groups should find at least one section that aligns with their preferred play style, but I'd advise against skimming the book. There is a lot of detail here, and some of the sections can be incredibly dense.
There are a range of alternate styles for Mage Chronicles but they aren't going to be to everyone's tastes. However, it is easy to cherry pick ideas and plot devices from all chapters. The writing is uniformly good, although the artwork is the usual mishmash of quality.
The section of styles offered did fire my imagination. The Noir section was very cool, especially as I've been on a Dresden kick for a while, but you'll be able to play almost anything from here. Second section deals with some of the variant magical systems, which gives players a chance to really develop a personal style, and build a strong paradigm (for those of you who like Ascension). I'll be using the Weird Science section in my next game. Lastly, there are some insights into the developers own chronicles and their highpoints. These designers notes are really interesting as you see how the games designers reshape the product line to suit their needs. Again, a huge number of ideas just waiting to be stolen - er, reworked and attributed.
Products like this are difficult to review, because what works for me and my group may not work for yours. This is worth the price, even if you are running Old World of Darkness. On a final note, the Epilogue bears some careful reading as it provides some ambiguous discussion on the future of the White Wolf product line. Read it and speculate at your own peril - I won't say any more.
[4 of 5 Stars!]