I read this book when I was younger and just loved the whole series. Given how quickly I've just ripped through this book I think I may need to keep an eye out for the rest of them to be 'easy readers.' 
Definitely some bits that might be scary for a younger reader, but I'd still recommend it! Now I've read it, it's going on the shelf in my (year 4) classroom for any curious kiddos to have a go at :)   
I feel like there are elements of this book,

specifically sections about the 'slaughterers' and maybe the bit about the trogs, and later how some characters talk about the woodtrolls

, that could be used to initiate conversations with kids about discrimination - racial and gender-based.