In three days, I picked up and finished Lost Light by Michael Connelly. I read it because it was a NYTBS, says so right on the spine. I’ve been working on the subplot of my own first story so I paid close attention to his subplots.
Subplots can build story or character or both. The better ones do both. The best ones wrap around to play into the crises and resolution. Lost Light did that with the two surprises at the end both coming from the subplots but still being very important to the story line overall. Nicely done.