Young William is instantly likeable, his love and dedication to his mother admirable. I did wonder on occasion just what child services thought they were doing. His journey into the other realm is expected as the synopsis is quite clear and he gathers friends that have powers that are predictably useful if he can only get them home to help his mother. The first stages of the journey take a long time, weeks, and it's a bit of a stretch to think this small boy (no matter how strong-willed and intelligent) would be holding it together with the thought of his mom dying without him at any moment. That being said, he does have his thrilling adventures along the way. Things obviously ramp up nicely once the magic starts and he's released from worrying about his mom. The more I read the more I enjoyed this book.
I can't see that it says this is YA fantasy (read it as an eBook) but a story about children with magical powers, dragons and few harrowing scenes even when there are murders and battles, I'd say it's very much in that realm. I'd encourage bunch to make it even more 'kid-friendly', especially the cover and market it in that genre. I can see this as a movie one day.