I let my little boy choose this for us to read together before bed each night. He is, like many of child these days, absolutely obsessed with Minecraft, and I can't exactly blame him. Even I got into it all over again for a little while upon introducing him to the game.
In truth, this book was a bit too advanced for him. He did not enjoy it all the much, and so towards the end was happy to let me read it on my own and simply tell him what happened. Bit of a copout, but for God's sake, he is not yet five, and I was getting tired of the exasperatingly slow pace.
I would say it is best suited for Minecraft fans somewhere between the ages of 9 and 12. Upper-primary school, very early high school. There was a decent amount of action, some moments of peril and even some relatively thrilling showdowns with the mobs. The writing was quite good, and Lafferty definitely turns in a good job, nailing all the tropes and terms and concepts as laid out in Minecraft lore. I would be very surprised if she wasn't herself a big fan of it.
There were a fair number of minor gripes, and I definitely feel like the pacing could have been a little faster, and also that the story would have benefitted by exploring some more interesting questions - eg, Uncle Nicholas's theorised attempts to communicate with endermen - rather than just turning into a predictable "escape from the Nether" adventure.
But for what it is, I think it's a perfectly adequate novel.