This is a nicely done effort, well illustrated and complete. For me the most useful feature was the maps of the hidden "bonus levels" in each realm, indicating the best path through each and thus allowing me to unlock the secret characters. Being able to unlock these characters is essential if, like me, you want to be able to say you took the game to the limit. (On the other hand, if I had to use the strategy guide to get through them, can I really say I've mastered the game? Oh, well.)
This book also clarifies a few of the finer points of strategy. For instance, you shouldn't grab that Turbo powerup right away if your turbo-charge is already loaded to the max -- otherwise the power-up will be ignored *and* wasted. Instead, go ahead and use your turbo-charge in a fight and *then* grab the Turbo power-up for an instant recharge. This kind of insight is nice to have.
On the downside is the small size of the screenshots. They are somewhat unclear. The level maps could probably also stand to be a bit clearer, but they are certainly acceptable.
In all, a very fine book. "Gauntlet: Dark Legacy" is not a difficult game to complete, but if you'd like to be able to enjoy all of its elements then this book would certainly be to your advantage. At the same time I would recommend that you locate the walk-throughs available on the Internet. There are also Web resources giving bonus-level maps that are not as polished as those in this book but are still useful.