Took me a minute to figure out the upgrade system, but that was a consequence of the sub-theme. The pacing was a bit off, I thought it would be really slow until I fully understood the upgrade system, then it was super fast. That's a very fixable thing though.
This would be really cool scaled up. It reminded me of a painting incremental from a while ago, but with a cool digital theme. Not very interactive past the first 2 stages though.
Is there any way to know when I've exhausted an area for books? After you find a few, your Explore success rate goes down, but I'm not sure when I should stop wasting gold somewhere.