The Woodsword and Stonesword books are awesome Minecraft early chapter books. My son is hooked, for sure, and each time a new one comes out we have to rush to Old Firehouse Books to snag it. The characters are fun and engaging and they have a lot rich experiences outside of the game, each book has a little morality play that goes along with it - usually having to do with inclusion or patience or mindfulness or setting the right goals. Like most things in Minecraft, it is what you make of it, but the fiction books they come out with are really hopeful and helpful in ways that young readers pick up on without it being heavy-handed.
Mobs Rule! is good, but not as good as the first book in the series (as is typical with a longer arc). The story (both in-game and out) was short and didn't have as much to it as some of the other books do... and there wasn't really an A/B narrative that followed more characters. They are all pretty much grouped together into in game/out of game on this one. There's absolutely room to expand on the teachers and that should have been done here, but maybe there's more to the arc coming up that I don't know about.
There was sort of a retcon reset of what the teachers knew in the transition from Woodsword to Stonesword, and I was always hoping that the backstory would hash itself out a bit as we went along. In any case, these are well worth your time and your kiddos' time to investigate and explore and might even inspire them to craft their own stuff based on what they're reading.