By Joan Slonczewski.
Definitely not as good as A Door Into Ocean or The Children Star.
The repeated explanations of meiosis and pre-natal germ cell development is... repetitive, and not really an interesting part of the story, for one thing. For another, the parts of "The Web" (a sort of Sharer philosophy text which is really a fairly brief narration by Cassi, Berenice's adopted daughter from the first book, sort of) read like a thinly veiled and insane philosophy text. The innocence of the Sharers, and whatever else that was attractive about the other two books, really isn't here. The story lines feel disjointed, jumping between Raincloud and Blackbear's plots, and the Sharers are barely present until the end. I had a hard time accepting that their culture could have changed so much as to allow the apparent concessions that the existence of Elysium involved, but there it is. When they do show up, their culture still doesn't ring true.
The machines also seem flat and poorly characterized; only a couple stand out and seem to be extreme examples. Little insight into their culture is given; much instead goes on behind the scenes.
The frequent hints at sex scenes (between Raincloud and her husband) were unappetizing and unwanted; there was very little so blatant in the other two books. (I wonder why she changed in this one? Perhaps it didn't work out well, since A Door Into Ocean came first and The Children Star came after.)
It explains some background and a couple rather specific references in The Children Star, but it's not really worth reading.