We got this book for our kids, but I don't think either one read it (yet). So I did, and that's why it's the YA version. I'm not usually big on YA novels (they seem much more focused on commerce than literature, more of a market than a niche).
Anyway, Stevenson's story is an important one, one well worth reading about (probably the adult version, to be honest) but he's a lawyer, and lamentably, he writes like one. It gets bogged down a lot in this meeting, that meeting, etc. For a YA novel, there's a lot of stuff it's hard to imagine kids caring about or reading through with gusto.
But again, the subject matter is important enough to make it worth the occasional slog. Stevenson dedicated his career to fighting for people on death row, and whether you think the death penalty is useful or not (I vote not, for all the usual reasons--mistakes are made, innocents die, it costs too much, it takes too long, it doesn't deter the next murderer, etc.) it's important to understand the topic more thoroughly than most people do.
Stevenson never gets too much into the moral side of things (in this version) but he clearly wants to save everyone on death row, regardless of guilt, and in particular children who are tried as adults and sentenced to death (or, later, life without parole).
It's admirable, given everyone in that situation had basically zero chance of making the right decisions based not their background and life circumstances, and in most cases, one bad decision (often "hanging with the wrong crowd") gets them into a situation that the state they live in is going to kill them for.
Stevenson, to his immense credit, is not having it. But he's a lawyer, and these things are done legally, (and slowly, and meticulously) so it's not a thrilling ride to read about sometimes. But it's important, and he sticks it out even when it seems hopeless for his cases--he's doing this mainly in Alabama, so it all seems hopeless, because, well, it's Alabama.
An important book, if not a thrilling page-turner. If this topic interests you, and you aren't a kid, I'd suggest the adult version of the book, to get the whole story.