I would not give an 8 year old Phillip Pullman even if they are a fantastic reader - totally spoils it for later when they can appreciate the very adult themes of the book. There are so many brilliant books for this age. Diana Wynn Jones is amazing. Julia Golding 'Diamond of Drury Lane', the Ingo books, anything by Cornelia Funke, Roman mystery series etc. I speak as someone who had a very precocious reader and as a teacher. Don't make them run before they can walk - even amazing readers need to read inside their age band. Older books normally have themes unsuitable, or difficult for younger children to relate to. I found the 8-10 age quite difficult in terms of this, but there are loads of books out there if you look hard enough.