In the final book of the Species Imperative trilogy, Mac travels to the
desolate planet of Myriam in search of answers. The Ro have revealed themselves to be bound by an imperative to migrate across other species' territories, and the Dhryn are their tools. Leaving behind her friend Emily -- who has been deeply damaged by the Ro -- in order to continue her research into a species that may have survived the Dhryn's depredation 3,000 years ago, Mac sets out without a little bit of trepidation.
This is a fine conclusion to a science fiction series that has had a refreshing emphasis on biology instead of technology. There are still problems with exposition in this volume, though, which make having read the first two utterly essential. Mac's an engaging protagonist and readers will be pulling for her to succeed. (May, 464 pp., $24.95)