Diadem #3: Book of Magic, by John Peel
Now on Dondar, a planet very close to the inner Diadem, Score, Helaine, and Pixel know that they are close to the end of their journey. Soon they will find out why they are being trained as weapons and herded to the center of the Diadem.
On Dondar, they encounter the ultimate of fantasy creatures: unicorns. The unicorns are extremely distrusting of humans, since most magic users want them just for their horns, but the trio manages to gain the trust of the unicorn herd.
The first half of the book is taken up with defeating Dondar's warlord magician, and the second half focuses on the shadowy enemy mentioned in the first two books of the series. Score, Helaine, and Pixel finally learn who they are, why they were sent from their home worlds, and who has left them the various puzzles they've found in their travels.
The ending of this first adventure is a little anticlimactic, as the battle doesn't live up to it being foreshadowed for three books, but it's a satisfactory resolution. Peel ends this book on another cliffhanger, as he sends the trio on a new adventure with their newest friends, the unicorns.
4/5.