The appeal to me was first, the book was written by Terry Pratchett; second, it was first published when Pratchett was 17-years-old, and third, it was revised by Pratchett, age 43, when the book was re-released.
Pratchett said in 1992 when the book was republished, "I wrote that in the days when I thought fantasy was all about battles and kings. Now I'm inclined to think that the real concerns of fantasy ought to be about not having battles, and doing without kings." That was my final summarizing thought when I finished the book - This book is about battles.
Pratchett's humor is evident and the story was okay, it just wasn't one of my favorite. I can see how it may be interesting for someone in Jr. High.