I've know about Small Steps for a while now, but I only got around to reading it because I thought the nine-year-old might like it. When I showed up to her house she already had a copy. I've finished, she's only part way through (and she doesn't know who Britney Spears is).
It was good. I got very nervous for Armpit in the middle and the ending is more ambiguous than I would have liked (also a little rushed, there's not a lot of time after the climax of the story).
Though I doubt it will ever happen, I could see the story making a good movie. I normally see books and their film adaptations as totally separate (eg I don't picture Daniel Radcliffe when I reread the Harry Potter series), but Brenden Jefferson kept popping into my head as X-Ray. I also pictured Zendaya as Kaira and Tatiana Maslany as Detective Newberg.
I think Sachar did a good job handling race in the book (but I'm not Black so I maybe missed something). There were a couple of times where everything Chinese was labelled "exotic," and I'm not here for that. There's also a character with cerebral palsy. I can't speak to how accurate her representation was in the book, but she's definitely a great character.
I enjoyed Small Steps almost as much as I liked Holes (which is saying something since Holes is definitely a childhood favorite). I'm not sure Sachar would ever revisit Armpit's story, but I'd love a sequel to this sequel.