At 16, Rhine is taken, stolen by Gatherers and crowded into a van with other stolen girls. She and two others are chosen out of that van to be wives for the wealthy Linden Ashby, to keep him company and bear his children until the virus takes them all, Linden at 25 and the girls at 20. Rhine is desperate to escape, to get back to Manhattan and her twin brother, to leave behind the opulent fakery of Linden's world and return to what she knows is real. 
 Rhine's younger sister-wife, Cecily, takes readily to marriage, eager to bear Linden's children and please him in any way she can; her older sister-wife, Jenna, remains emotionally distant from Linden but becomes a true friend to Rhine. Rhine is uncertain: Linden is not loathsome, and she's quickly becoming his favorite, but she still has no desire to be married to him and fulfill that role. Her affections are growing in a different, dangerous direction, and her father-in-law will stop at nothing to ensure Rhine's cooperation. 
 The premise--that all breeding needs to be done by teens to ensure humanity's survival--is similar to Megan McCafferty's Bumped, but that's where the similarities end. The darkness of this book is more on par with Bacagalupi's Ship Breaker or the bleakness of Atwood's Oryx and Crake (Handmaid's Tale is more similar in plot, but O&C has a darker tone, to me). 
 Dystopian: kind of. The virus is killing all males at 25 and females at 20. The dystopia isn't a large-scale political thing; it's more on a micro-level inside the mansion, with the three wives locked on one floor to be Linden's companions in every sense of the word. Humanity got to this point after science managed to cure cancer and other diseases, but unleashed the virus in its wake. Some sort of disaster happened that flooded every continent except North America, work is scarce, children are orphaned at young ages (since their parents die at 20/25)--but it's hard to get worked up about the post-apocalyptic elements because nearly the whole book takes place inside the house, isolated from the problems affecting the world outside. 
 Older teens looking for more substance than the other recent dystopian romances may enjoy this; best guess says the rest of the trilogy will show more of the romance and post-apocalyptic world setting.