I think this is a good change overall. Mojang has been putting a lot of effort into getting people to explore the world over the past few updates, and this feels like the next step of that. Making book trades biome dependent forces players that want to maximise to go out into the world, and maybe even set up infrastructure to make travelling less tedious.

I do worry about the anvil costs, now that you’re always going to have to combine books together to level them up. The “Too expensive” message adds nothing to the game, and only punishes players for a mechanic that was almost completely redundant the update immediately after the redesign (anvil rework in 1.8, mending added in 1.9).