Before you go on, I just want to say that much like the Nintendo Power Guide, Prima's guide doesn't have a proper Pokedex. It's got a list of all the Pokemon you can catch, but no full Pokedex full of the moves lists, stats, evolution, etc. This has come to be expected of Pokemon guides, but keep in mind that if you want a guide for the Pokedex, you won't get it here and you won't get it from Nintendo Power's Guide either.
Third party guides are always something of a debate. On one hand, they just look better than some of the first party guides and often provide information that isn't normally found within a first party guides pages. On the other hand, they're third party. It's not straight from the pros. Prima is pretty well known for pumping out fairly good Pokemon guides (save for their Fire Red/Leaf Green guide), and I expected this to be a brilliant guide. It's not bad, but for a Pokemon guide as big and thick as this, you expected they'd cover so much more of the game than they did.
The introduction chapter is nice but long. Much like Nintendo Power's guide there's a lot of information to swallow here. Newcomers would do best to start here, but really, there's nothing that anyone who has played a Pokemon game doesn't know. If you've been with Pokemon for a while, most of it should be pretty natural to you now. Still, the information contained here isn't bad. It's just that Pokemon hasn't changed so much that those who've been playing don't know this already.
The walkthrough, the meat and bones of any strategy guide is where things get a little hectic and the guide reaches a high point. The walkthrough isn't perfect, nor is it as well organized as the walkthrough by Nintendo Power, but it definitely works well and can get you through the adventure. It feels like it lacks, detail however. The guide is written in a step by step fashion. That is it says: Step 1, and then goes on to explain step one. The problem with how this guide utilized its step by step walkthrough is that I know what to DO, but not really WHERE I do it, and the screenshots don't really help either. So its great that the walkthrough is written like this, but it would've been nice if like Nintendo Power they told you where to do this stuff. They detail all the return trip stuff in some nice detail, though. However, there are moments when in the walkthrough the guide will lead you somewhere only to tell you you can't do anything and to turn around. It's really annoying to go all that way only to have to turn around. Also, the guide tells you what items can be obtained in an area, but it doesn't show you where the items are on the map. It points berries and the like, but that's about it. While it helps you find Gym Leaders, the suggestions they make are also not all that helpful. Again, though, I can't be too upset with this considering this is Pokemon, where as long as you know your opponents type, putting together your own strategy should be no problem at all.
Really, the walkthrough isn't bad, but it does feel like it's lacking detail from time to time. Such as the maps looking like generic screenshots or the lack of actual screenshots. Yet what you get from the walkthrough is really helpful and detailed, even when it seems like its not. The Prima guide really is a good guide to have. Perhaps it just doesn't have that flash.
All the stuff after the walkthrough like the contests and the wi-fi connection is also really really helpful. Yet the Pokemon lists is really not. They'll show you all the Pokemon you can catch and then tell you where to catch them. That's it. No moves list or anything. To an extent it's pretty useless, but I suppose you could make do. However, the coverage of the wireless connection and contests is more than willing to make up for the loss. Especially the wi-fi connection as its pretty new and Prima devoted an entire section to it.
Afterwards we get into the charts and appendices. All the stuff is here, but like a lot of appendices in guides, there's a lot of it, which means a lot of page flipping. The guide will already have you flipping pages as it is at 296 pages (most of which is actually just unfilled space, you're really not getting anything here that isn't in Nintendo Power's Thinner guide). At least you can look back there if you're unsure of a move, TM or HM, and the like.
Overall the Prima guide is actually a pretty good guide. There's not a whole lot here that isn't in the Nintendo Power guide. If you're looking for a better organized guide then go with Nintendo Power, but that shouldn't suggest in anyway that the Prima guide is bad. Again, though, it's becoming a pain to always have to wait for a separate Pokedex to come out, and here it's no exception. Prima will release a Pokedex sometime in May, so if you need one, that's when you can get one.