This book, written like a history text interspersed with the maxims and poems of Minnipin heroes, is a very gentle fantasy novel for young readers. For lack of a better comparison, it really reminded me a lot of some of the fantasy cartoons I watched as a kid - The Gummi Bears, The Adventures of Teddy Ruxpin, and The Smurfs, for example - which are set in vaguely medieval-inspired fantasy kingdoms with no particularly complicated mythology behind them. The characters are easy to differentiate from one another, owing to the specific traits and talents each one has, and though they are not children, they are child-like, both in their willingness to believe new things, and their feelings of powerlessness in the face of unmoving authority. There are definite dangers, including battle scenes in the later chapters of the book, but the story always feels comfortably contained and cozy even at the height of the excitement.
The book has some problems, which I think are actually more pronounced because of the Newbery Honor sticker on the cover. The writing just never felt completely tightened up to me, almost as though the author didn't quite reach the heart of what she wanted the story to convey. The setting is also vague. Most of the other fantasy books I've read so far have done some level of world-building from the ground up. This story felt more like it had been written as part of a roleplaying game where the author chose a few elements out of a hat and wrote a fantasy story based on them. I think this kind of simplicity would have appealed to me as a kid, and might have actually gotten me to read this book, but after having read things like The Hobbit and Harry Potter, it felt weird not to be given pages and pages of detailed exposition about the setting. What is included is fine, but all the preliminary details felt like a means to an end instead of an integral part of the story in their own right. I am not usually big on setting, which might be another reason fantasy doesn't tend to be my favorite, but kids who do focus a lot on the details of fictitious societies might not find enough meat here.
I enjoyed The Gammage Cup and will look for the sequel at some point in the future. For kids who want to try fantasy but don't like scary stories, or who have read The Hobbit but aren't yet prepared for Lord of the Rings, this is the ideal book. It would also make a nice read-aloud provided you can pronounce the abbreviation names and don't mind occasionally having to show an illustration to your listeners so they don't miss anything.