This book stood out to me because the characters were well-developed and easily distinguished from one another. The clan dispute is understandable-- the Cloudfoots inhabit and better territory, and the Northenders want it-- but easily resolved when the squirrels realize that they all can work together. The author's note about the current endangerment of native red squirrels in Europe because of an earlier importation of gray squirrels adds a sense of realism to the struggle.
The supporting characters are interesting as well. The dogs who patrol the park don't eat squirrels and keep other dogs from doing so, although they can't be everywhere all the time, and one squirrel, who has not been a sympathetic character, does come to grief at the paws of an overzealous Scottie. There are also a few deaths during skirmishes, which makes this an older middle grade book despite the appealing fellow on the cover.
Know a child who won't read anything but Erin Hunter's The Warriors series? This is a great book to read until the next book comes out!