I read both of these books recently and I feel very similarly to you. Both very good books that I enjoyed, but the second one had some clearer flaws. Those flaws didn't ruin the reading experience, but did mean after it was over I felt less satisfied.

I agree with your review, and have one thing to add. (And thank you for giving me the opportunity! I've been mulling this over for a while and didn't know where to share my thoughts.)

Spoilers follow! [Edit: MAJOR spoilers. Do not click and read the below if you haven't read the books and don't want them spoiled.]

>!The OP has pointed out how the structures have some parallels. One more major parallel is how a technology introduced earlier on in the book is then responsible for the climatic ending where multiple sentient species are able to come to a joint understanding. In Time it's the "smart virus" that is used to help the humans feel kinship with the spiders and avert disaster. In Ruin it's the brain interface that allows Kern to make real contact with the The Many and avert disaster.!<

>!In the first CoT book, the virus is fundamental to the plot. It drives the entire novel, since it's what allows the spiders to evolve into an advanced species and contributes to their whole memory-transfer ability. So when that virus is used to bring the humans into a feeling of kinship with the spiders it feels like a really logical conclusion to the storyline.!<

>!The problem in the second CoR book is that the brain-interface technology is not fundamental to the plot. In fact, many if not most of the scenes where the book explores that technology feel ancillary from what is going on. Yes, it's interesting and important how that technology gives Kern the ability to "feel" emotions again, and the way she those emotions distract her does have plot relevancy. But the whole book could have definitely been written with all of these scenes removed, except for (of course) the climax.!<

>!So, the conclusion of the second book felt less satisfying to me than that of the first. In retrospect it became clear that the author had added this technological diversion side-plot in order to deliver that conclusion, rather than having told an organic story with an organic conclusion. (In other terms, it made the "author's hand" a little too obvious.) !<

Anyway, that's not saying the second book wasn't a good book or that I didn't enjoy it. Just a plot point (a major one) that didn't work for me as well as it did in the first book.