I've just about finished the book, and by that I mean i'm on page 643 of 710. I also didn't read every single page. This is similar to some of the wine encyclopedias out there IMHO. I read all the general information chapters and the info at the start of each section for areas of Bordeaux. I then read the entries for the top chateaux for each region. And even then that's a lot. Information is great. Even explaining the the vineyard management and winery practices for each property if he was able to get that information. Not just "hey this is an important chateau and I tasted a couple of their wines." Brook let's us know his tasting notes for various vintages of the wines.
Brook also gives you a perspective of some of the inner workings of Bordeaux. He does this without getting snarky like some other writers. He definitely has an opinion of this and also about the chateaux in general, but he's not here to necessarily bash anyone. Not every chateaux is making world class wine when they should and he'll at least let you know that in a professional way.
Granted, the book is somewhat dated at this point, but what wine book isn't after a few years? The general information is still valid. It's not like the region has undergone a radical change in laws or how they make wine. What few legal things that have happened since 2007 aren't critical to the book, and he even talks about some of this (Saint Emilion's Classification being in flux at the time for one example). Those things can easily be found on the 'net. And there will have been some ownership changes, winemaker changes, etc., but again, not like it takes away from the overall information in the book.
If you need to delve deeper into Bordeaux, then this book will deliver.