First of all, the guide has a very detailed and easy to use walkthrough. I loved it. Easy to follow and easy to read with great detailed maps and plenty of screenshots (which you'll undoubtably need!). There is a maps section before the walkthrough and then they show the maps again before each section of the walkthrough, which makes for far less page flipping.
The Metroid Prime section gives you the run down on everything you need for all of Samus' abilities and how to obtain them in this highly detailed walkthrough. The screenshots are clear although at times they can be a bit darker than others. Some screens are actually very hard to depict what they're trying to tell you even with the text standing out. I wouldn't consider the terrain you venture through in Metroid Prime to be quite that dark.
The Metroid Fusion section of this guide is very useful if you want to complete the entire game. Much like Super Metroid, Metroid Fusion maps seemed more like a grid and Prima did a very good job in these maps by highlighting hidden areas along the way. Using this guide it is nearly impossible to get yourself lost (although the game makes sure you don't get lost either...). Again, a run down on all Samus' abilities and a full walkthrough to help you get everything you need to defeat SA-X and save the universe! A great companion in deed. The screens are still a little darker in this section but because of the fact that Metroid Fusion has a bit more lighting in some areas than Metroid Prime, you can much more easily depict these.
My gripes with the guide. Well first of all, for Metroid Fusion it doesn't depict how to get all the different endings of the game. I do not believe they did this in Metroid Prime either. Also, there is no walkthrough for the original Metroid. This isn't too bad of a problem but the first Metroid game presents probably one of the greatest challenges in the series (aside from Prime of course) and I need more than just basic "tips" that I've already come to learn by playing other Metroid titles. My thrid gripe of course is the dark screens but they are crystal clear and you shouldn't have a problem trying to make out anything in the Metroid Fusion section.
Overall, this guide is probably your best friend in completing both of these titles. It's nice to see that there was a guide publisher that took Metroid Fusion into consideration. Both guides are good and WILL help you find everything with little hassle.
So...
The Good
+Complete walkthrough for Metroid Prime and Fusion
+Detailed Maps for both section
+Nice thorough walkthrough for both sections
+Crystal clear screenshots
The Bad
-Game endings aren't revealed
-Metroid Prime screens are a little dark at times
-No NES Metroid walkthrough, just "Tips" on how to go through the game.
While the last con isn't a problem it would've still been nice to include a short walkthrough at the least being that it is a secret of the game.