Warriors #1: Into the Wild

Into the Wild opens Erin Hunter's Warriors series with Rusty, a house cat who leaves his easy indoor life and walks into a forest governed by four Clans and a strict warrior code. ThunderClan, the group he ends up joining, is under pressure from a ShadowClan that keeps gaining ground, and the book spends its 147 pages establishing how much structure, and how much danger, exists in a world most readers will assume is just cats in a forest. Harper Collins lists it for ages 6 to 10, and at under 150 pages it's a reasonable length for a first fantasy chapter book.

The appeal for this age group is watching an outsider learn the rules of a closed society from scratch, right alongside the reader, as Rusty works toward becoming a warrior apprentice and picks up Clan law, territory boundaries, and rank the hard way. Loyalty, bravery, and honor come up as lived problems for Rusty rather than lessons stated outright, which gives a discussion-minded parent something to talk about after chapters rather than during them. As the first book in a long-running series, it's built to end with more story clearly ahead rather than wrapping up on its own.