I originally bought this book for my daughter, but it turned out to be a little old for her, so I'll keep it for later. It's a lovely tale, well-written, with believable, individual and likeable characters and plenty of adventure to keep the reader interested.
Young Kel has a talent that many children would love to have - being able to disappear against the background so that no one can see him. His talent makes him valuable to his country, which faces attack from a neighbour with a terrifying new weapon. It's this weapon, I'm afraid, that stopped me giving the full five stars to this story. Had it been a magical weapon, I would have been happier, but the mixture of high-technology with medieval setting didn't feel right to me. A younger audience may not notice the anachronism.
However, that was my only quibble with what is otherwise a great story. I highly recommend it to any young reader (or older reader) who loves fantasy adventure.