The title may be a bit misleading -- this really doesn't seem to be a reference guide to restoring BMW's as much as it is an encyclopedia of BMW motorcycles. If you're looking for a book to guide you through a detailed restoration, this isn't it. But it is, nevertheless, an excellent historical reference to all things BMW.
There are many wonderful illustrations, photographs and copies of old advertisements and even bills of sale. If only there was a book like this for every vintage marque... If you are seriously considering purchasing a vintage BMW for restoration, you need this book -- just be aware of its limitations. Four stars for any BMW "airhead" lover; three otherwise.