The Post-Birthday World by Lionel Shriver

I read this book for my book group. It's not a book I would have normally picked up, nor would I even be aware of it had someone else not recommended it. I always enjoy reading things outside my normal scope, so on that level, it was enjoyable. But, if asked in one word whether I liked this book or not, my answer would simply be no.
Shriver writes about a lot of compelling topics. She brings to the forefront issues in relationships that are worth pondering. She did make me stop and evaluate moments in my own relationship. On that level, I found the story engaging. (oh, and it is very sexual. A LOT of the relationship angst dwells in minutiae of long-term sexual relations. I wasn't offended, but I honestly didn't need to know that much detail about anybody's sex life. - but I do give Shriver kudos for writing so blatantly about sex.)
In addition, the format of the book is relatively unique. If you have seen the movie Sliding Doors with Gwyneth Paltrow it has a similar layout. In the novel the main character has a choice to make in the first chapter - whether to kiss a man who is not her significant other. The rest of the book alternates chapters based on her decision. The first is her life having kissed Ramsey Acton, famous snooker player in London. The second is her life having resisted the urge.
Here's my problem with the book though. In order to follow the two story lines to their logical conclusions, the book becomes trite. The author essentially had to create polar opposite story lines to keep the reader reading. Reading the same information in each chapter would not have logically worked. In addition, it would be too easy for the scenario in which she cheated on Lawrence to end badly and the scenario in which she was faithful to end well. But it is almost more obvious to reverse those scenarios: she cheats, yet it all works out in the end and she's faithful, but in fact that was not the right choice. I spent most of the book just waiting for it to be over to see if I was correct in my assumptions. On a overarching level, I was.
Finally, I didn't like the main character (considering that I couldn't even remember her name until just now tells you how memorable she was). Irina McGovern has to depend on her relationship with a man. Admittedly relationships do define much of who were are but I grew to dislike the character in both story lines. She needed to grow a back bone, stand up for herself, and leave both of the men. It's hard to read 500 pages when you know you're just going to get repeatedly annoyed at the protagonist.
Now, I'm just curious to get to book group and see if everyone else loved the book. If they did, I may be sitting quietly for most of the evening, because I'm not sure I will have much to add that's positive.