While I've enjoyed all the previous books, I didn't find them all that substantial beyond light, enjoyable fun. Heaven's River definitely elevates the quality in comparison to its predecessors, and it held my interest the whole way through.

I think the main change is the introduction of a creative and thought-provoking new race of aliens and the topopolis megastructure they inhabit. The aliens themselves weren't particularly unique, but the concept of a pre-industrial civilization that had previously advanced to the level of creating an immense megastructure and an advanced AI to manage it before largely regressing. Trying to understand a civilization that has an advanced overseer who is effectively standing in for a god to a culture, having a subset of the civilization that has not regressed and is still using high speed rale (far more advanced than ours) while the rest of the civilization is moving around on carts, transporting themselves by boat and living a more simple life. It's a fascinating concept to me.

That said, I also didn't find the continued conflict between the factions of bobs very compelling, nor the conflicts with humanity and the inevitable meltdown being foreshadowed. I also felt like the big twist at the end was rather predictable, and the conclusion was somewhat anticlimactic and unsatisfying.

Still, I'm stoked to read the text book and hope Taylor keeps growing. The series, and especially the author, have so much potential, I can't wait to watch.