This article linked near the bottom is pretty interesting w.r.t. the origin of eukaryotes. IANA biologist, but it seems to make a pretty good case that taking on mitochondria led directly to a lot of the other eukaryotic complexity. I wasn't previously convinced why it couldn't have gone the other way. https://elifesciences.org/articles/81033
This is the thesis of the book “The Vital Question” by Nick Lane. It’s a pretty interesting read. At points the book was slightly beyond my reach in comprehension but I still enjoyed it.
