Really solid. I liked this as a cap to the quasi Arbai series, and the series in general as fun sci-fi-philosophy. I think the end revelation came a bit quick (the thing that let Fringe figure out what she needed)...and then it turned out she didn't need to do anything because the one sane professor did the thing? That bit was a bit confusing as to what her intent was for what actually happened. It seemed like the the thing Fringe did wound up being ultimately pointless with respect to the "big bads", very confusing.

Endings seem to be a weakness for Tepper - not enough to detract from the story as a whole, but I've found that I usually come across a section or two that I would have appreciated being revised in each of her books' endings.