Having got the first guide and being slightly disappointed with it, I soon sold it. However when I heard that the second one was coming out I read the description on Amazon, and ordered it and I must say that I'm not disappointed with this one at all.
It contains many sections, including the Kanto walkthrough which is very detailed, but it doesn't contain the Trainers Pokemon, which I'm not too fussed about but others might be. The second section is made up of smaller ones, like the Pokewalker guide, and the National Pokedex Completion guide. I must say that all of these are very useful, but not as useful as the main part of the guide - the National Pokedex.
Each Pokemon has half a page, and on that it lists where to get them on Pokemon Diamond, Pearl, Platinum, HeartGold and SoulSilver. Along with this it includes what moves it learns, including TM's, Egg Moves, and ones learnt through Move Maniacs. Plus it includes the walking picture, the footprint, size comparison, Pokewalker picture, and the difference between a male and female.
After this it has the item index, which is useful if you're looking for a particular item.
The book is as well 552 pages, which on its own makes you think how much info they put in. And I can tell you that they crammed as much information in as possible to this guide. A must buy if you've got any of the DS Pokemon games as it contains the info in the Pokedex for all of the DS games.
Great buy, and has helped me tonnes so far!