This is an absolutely exhaustive history of bicycle gearing. I cannot imagine another book getting even close to the level of detail found here. If you have a hard core interest in bicycle gearing or bicycle history, you need to read this. I was totally geeking out whenever the discussion came around to a particular manufacturer or piece of hardware that I had personally used (or suffered).
I have a few complaints, but certainly nothing that would tempt me to drop a star rating. I wish that the book had gone through one more round of proofing. There were a handful of typos and cut off captions that really should have been caught before printing. By nature of the organization of the chapters and sections, certain histories were repeated. And sometimes the level of specific detail became a bit much, even for me.