This book in my opinion is one of the best of the DS9 books in the relaunch series. The action couldn't be better, the machinations of Section 31 have fascinated me since I first heard of them on the TV series and the plots which are not only action driven but character driven are put together very well. I sincerely hope that more Section 31 based DS9 books will come out in the future.
As we know from the television series, Sloan is dead so another mysterious character known as Cole fills his spot. Cole mysteriously appears in Dr. Bashir's room asking him questions and in a round and about way gets him to go on a dangerous covert mission for Section 31. This mission will challenge and test Dr. Bashir in ways he has never experienced before. Dr. Bashir must match wits with another genetically enhanced individual called Dr. Ethan who used to work for Section 31 but betrayed them. Dr. Ethan is a eugenicist who took over a planet where he breeds Jimhadar soldiers loyal to him and conducts genetic experiments making clones and designing weapons to destroy others who are deemed inferior. Ezri, Ro Lauren and Taran'atar all go with him to the planet Sindorin to assist in bringing Dr. Ethan to justice, but he also would like to crush Section 31. Sindorin is where most of the story takes place. There are quite a few good firefights and suspence as well as some very good dialogue.
The book also advances other plots from previous books as well. By the way, Jake is still lost and Cassidy still didn't have the baby yet.