Crystal Mentality is the continuation of Crystal Society. Overall, it is less fun than the first, but still enjoyable.
The external conflict in this one is boring, I think. It takes place entirely on the alien Xenocruiser and on Mars. There are necessarily, then, fewer interesting humans for Crystal to encounter. Those that Crystal does encounter, she pretty much just manipulates with the utmost ease. They never have agency compared to Crystal, or are threats compared to her, or really even perceive her hostility.
On the other hand, the internal conflict in the book is excellent. The POV-agent within Crystal, Face, realizes that her goals and the goals of her siblings are ultimately not aligned -- she goes through an ontological shift, and realizes that her true enemies are Growth, Dream, and Vista. The most fun enemy, here, is Vision, the merged version of Dream and Vista, who therefore has twice the internal strength of Growth or Face. (Heart, of course, being the most human-facing entity, as well as the youngest, is a non-entity entirely.)
This reread was ultimately a bit slow for me; I kept dropping it for other things (see review of The First Law) because of the kinda cringe nature of the external conflict. But ultimately, I think it's a good book.