Like most of Gary Paulsen's novels, this is an easy-to-read and action-packed story which moves quickly from exciting event to exciting event. Francis is very likable, and his inexperience and immaturity make him very easy to relate to, even though his experiences are far removed from contemporary kids' lives. The dynamics of his relationship with Mr. Grimes are the driving force of the book, and they are made especially interesting by Mr. Grimes's dubious moral code, a problem which Francis must deal with more deeply as time goes on.
The main problem with using this book for educational purposes, I think, is that the story does not end with this volume. Rather, almost every question raised in the story - including whether Francis ever finds his way back to his family - is left unanswered, as there are four more titles in the series. It would be difficult to build a lesson plan based on what is essentially the introduction to a longer saga. Breaking the story up into parts is a wise choice on the part of the author and publisher, because it makes the story more easily digestible for young readers, but it also means this is the kind of book I'd recommend for supplemental pleasure reading, rather than for a more formal novel study.
Readers in grades 3 to 7 seeking adventure stories, and especially those who love westerns will devour this book, and they will probably be as eager as I am to dig into the sequels.