Firstly, let me say that I am a massive King and (obviously) a Dark Tower Junkie!
Sadly however, this book gives nothing new to the DT Series. As King himself stated, this book was never ear-marked for publication but was written by Robin Furth as a reference guide for King, for writting Volumes 5,6 and 7.
I have read the first four volumes many times and this book revealed no more to me than I already knew. This book contains:
1. Foreword by King,
2. Intro by Robin Furth,
3. A-Z index of characters with volume and page reference,
4. A-Z index of Mid-World Locations,
5. A-Z index of Locations in OUR world with D.T. references,
6. Chapter on 'sayings' and High Speach words used in the Novels,
7. 2 maps showing Rolands journey from Pricetown to Golgotha (DTI) and Shardiks Lair to Lud (DTII)
...and basically thats your lot! If you still think you need this book, try and have a look at a copy before you buy.
....But, the Tower IS closer and the Rose is still in terrible danger!!