I'm going to be honest. Not everyone is going to like this book. There are two major things that even fans of the series may have some difficulty with, and the first is lack of adventure. The second is a revelation that puts past relationships in this series in a new light, and will be discussed later. This reads like a coda to the Vorkosigan series--it travels up and down memory lane (fans of the series will love this), explores past events through viewpoints that we haven't seen, and talks an awful lot about relationships (especially relationships in the public eye), parenthood, grief (and grief's aftermaths), and romance between people who are no longer young. Being in my mid-forties (and in this book, that's Miles's age) and a parent of rapidly-growing children, I can appreciate this, but if you love the Vorkosigan series for its sprightly adventure aspect--this book may not be quite your cup of tea. 
 I love this book. In one of her comments on the Bujold List, the author describes it as a mashup between SF and women's fiction, and that is exactly right. However, none of the previous books have fallen into this category, so I think there are fans who are going to think it's kind of boring. But if you like SF, are as openminded as a Betan should be, and enjoy clever yet understated autumnal romances like Major Pettigrew's Last Stand, you will probably love it too. 
 The plot revolves around widowed Sergyaran Vicereine Cordelia Vorkosigan, as she draws Sergyar fleet Admiral Oliver Jole into a reproductive scheme sure to surprise, if not scandalize, everyone on the planet. (view spoiler)[One of the Big Reveals in this book is that Oliver Jole (first mentioned, I think, in The Vor Game as Aral's perfect and handsome young assistant--through Miles's viewpoint, we see him as more of a possible rival for parental attention, but, heh, no.) had been Aral's long-time lover, with Cordelia's support, and, in some cases, participation. Cordelia, with her practical (and hyperanalytical) Betan mind, sees Oliver as a co-spouse rather than an interloper, but the intimate aspect of their relationship ended shortly after Aral died. I think some readers are going to have a some trouble wrapping their minds around this revelation, given the views--from their initial romance through Miles's and Mark's views of their parents-- they've seen of Aral and Cordelia's relationship in past books. (hide spoiler)] How the relationship between the two of them progresses is also a large part of the book--and how their families, ambitions, and interests will fall in line with their plans presents much of the plot of this book. There are also some interesting side plots about a Cetagandan "discernment garden" and Sergyaran wildlife, and some less-interesting side plots about concrete and military contracting, which didn't go anywhere much although I kind of thought (or hoped?) it would. 
 This book has much the feel of a wrap-up to it. Unlike most of the books in this series, it would present a terrible entry-point. And while it doesn't exactly preclude other books in the Vorkosiverse, one hopes that this set of characters, at least, will get to enjoy their respective happy endings.