We had both books: LP fresh of the press and Thomas Bryn's book - THE guide to have. Thomas' had a new edition in february 2004. Best to take the most recent editions of guidebooks. The handbook is more interesting to read, so that's a must. You'll have plenty of time to read!
The trip is recommended to anyone: we found a british couple with 2 kids doing it! Don't be too easily discouraged, try to take the east-west trip (to avoid wagons full of tourists!).
This book is a decent rough guide and the only one of its kind. For that reason I rated it a three. It was sufficient for my trip on the railway, but I wouldn't call it a "Survival guide" as such. I'm usually a huge supporter of The Lonely Planet, but in this particular instance they have not done a supurb job.