Barrayar is, chronologically, the second book in the Miles Vorkosigan series, though it was written after the first few books of that series came out. It continues the story of Miles' mother, Cordelia Naismith (though now she's married, so it's really Cordelia Vorkosigan). It ends with a very young Miles, neatly tying into the beginning of Miles' story (which is what the rest of the series is about). Barrayar won a Hugo award, one of the highest awards in science fiction writing, and I will have to say that it was well-deserved. This is a fabulous book.
After leaving her home planet of Beta to marry Aral Vorkosigan on his home planet of Barrayar, Cordelia tries to settle into a Barrayaran retired nobles' life. Aral has retired from politics and wants to lead a quiet life with his new wife. Cordelia is pregnant with their son, and he just wants to live a happy life with her. Unfortunately, events transpire to make that impossible. The Emperor is dying and his grandson (the son died in Shards of Honor, the first book) is only four years old. A regent must be appointed, and Vorkosigan is the only one who would be agreeable to the majority of Counts. Thus, Cordelia and Aral's life is turned upside down when he assumes his new duties. There is plenty of political intrigue as other Counts scheme for power because Vorkosigan wants to bring Barrayar into the current century while the conservatives want things to stay as they are. These events even go so far as to really affect the unborn Miles in ways that will be familiar to long-time Vorkosigan fans, but which I won't spoil in case you've never read a Vorkosigan book.
This book is fascinating in many ways. First, as a fan of the series already (I've only got two books to go, not counting the new one that's coming out this summer), it was very interesting to see the characters I've known and loved for so long before they became the characters I've known. It is interesting to see them develop the attitudes that I'm familiar with. Simon Illyan (the head of Imperial Security in the series) starts out as captain of Aral's personal security force. Emperor Gregor, who we've only seen since he was seventeen, is now a four-year old child, aware of what's going on around him but not really understanding the political situation. A lot of the nobility would like to control him, especially through his mother.
Not only the characters, but there's also many events that have been referred to in the series that we finally get to see happen on screen. Biggest of these, of course, is what happens to Miles. We have been told many times what happened, but it's interesting to finally see it. Of course, there has also been a lot that hasn't been mentioned before, and those events are intriguing too. A lot of what we know is now coloured a different way now that we know the events that surrounded it. Some people have suggested that you should read this series chronologically, starting with Shards of Honor. I'm almost of the opinion that you should have a few Miles books under your belt before tackling these, just because it makes these books even more interesting than they already are.
The second reason the book is fascinating is because of the view of Barrayaran politics that we get. Cordelia is an outsider, and some of the practices on Barrayar are almost barbaric to her. There is very little genetic manipulation of offspring, for one. Mutants are killed as soon as they are born so they don't affect the gene pool. Some other political aspects are so different than what she's used to that she needs some coaching in how to deal with them. Thankfully, Aral's family is up to the task. It's interesting to see these from an outsider's point of view. I don't think the story would be nearly as effective if it was just a political tale told from within Barrayaran society. Some of the most priceless scenes come from this weird dichotomy.
For fans of romance, though, there is definitely some of that in here. This book continues to develop the relationship between Aral and Cordelia, showing how strong their love is as it withstands the pressures that politics places on it. Again, as with Shards of Honor, this is a mature romance, though because they are actually together now (unlike Shards), there are some playful moments as well. These are two character that the reader cares deeply about.
I couldn't put this book down. It has everything: action, romance, explosions, intrigue, great characters. This one is certainly worth a pick up. It also stands alone, as you don't need to read any of the other books to enjoy it. It helps to read the others (especially Shards of Honor), but it's not mandatory. Wonderful book.