I really enjoyed the book, particularly the protagonist, Jeth Seagrave. He's complicated, rough around the edges, sometimes cute and sometimes silly, and completely endearing. I think that girl and guy readers will like his point of view. It was sweet that he has a soft spot for his sister, Liz, and for little Cora. He reads Cora stories and kisses her goodnight and is totally big-brother kind of mushy with the little girl. So adorable.
I am such a huge science fiction fan, and Avalon didn't disappoint me in that regard. The world-building for humankind's future was really well done. The intricacies of metaspace (not to be revealed cause spoilers!) were really cool, albeit a little predictable, and still really otherworldly and interesting. The biology and physics needed to explain some of the plot points doesn't get too complex at any point - but it doesn't baby the reader, either, which I really respect.
I was only disappointed with the lack of depth in the side characters (except for Jeth's sister, Lizzie). Jeth's crew had the potential to be a really awesome group of misfits, like in Lydia Kang's Control or Gina Damico's Croak series. But they were flat, undeveloped teens without enough depth or anything to make them memorable. In the next book (yes, it's a trilogy!) I hope that changes. I want to know more about Shady's past, and laugh at more of Flynn's silly antics, and see if Celeste is jealous of Jeth's attraction to Sierra. However, that's my only small complaint.
Fans of sci-fi and action will really enjoy this book. In particular, if you liked The Paladin Prophecy, Control by Lydia Kang, and the Alex Rider series then you'll definitely like Avalon. I would recommend it for middle and high school readers, as well as adult fans of YA.