I just purchased this book today; I've read the first couple of pages and skimmed the rest. I find it to be quite interesting. Some tidbits and hghlights:

An overview of Gen Con 0, held in 1967 at Gygax's house.

The impact on Gen Con of various trends in the RPG industry, such as LARP, CCGs, d20, etc.

The bad blood between Gen Con and Origins, and how they buried the hatchet.

Gen Con peculiarities such as Uncle Duke & The Dragons, and Duct Tape Girl (don't ask; it must be seen to be truly appreciated).

A number of photographs, including a nice shot of FASA's 1994 Gen Con Shadowrun demo. Let's just say that many of the photos would also fit well in the "Who we are as gamers" thread. Want to see some real life chain mail bikinis being modeled? Check out page 108.

Insight and interviews with various Gen Con luminaries, including not only the obvious heavyweights such as Gygax and Arneson, but also artists like Phil Foglio and Larry Elmore, and writers like Tracy Hickman.

All in all an excellent volume, especially in concert with 30 Years of Adventure. I highly recommend it.