On the same road trip when I listened to The Year of the Flood, I also listened to Margaret Atwood's Oryx and Crake.
A lot of my enjoyment of a book comes from the narrator. Even if I didn't always love both narrators of Year of the Flood, they were distinct, and the point of view shifted often enough to keep one voice from going stale. In Oryx and Crake, we have only the voice of Snowman, gone mad with loneliness and grief.
Having read Year of the Flood first, the fact that Snowman is the only narrator also tips the author's hand that there will be no other people in this book. Much more than Robinson Crusoe or The Shining, Oryx and Crake is about what it's like to be the last man on Earth.
Oryx and Crake also suffered from the prequel problem (since I listened to the two books out of order): there were plenty of mysteries in the first book, and they don't all have to be explained away. Trying to understand without knowing is a part of life, and it's a part of the best fiction. Many of the scenes in Oryx and Crake I would have been most willing to cut involved the development of the technology that was taken for granted in Year of the Flood like ChickieNobs and pigoons.
Much like knowing the ending to a mystery novel, knowing a piece of the ending sapped some of the joy from Oryx and Crake. I'm not sure what I was hoping for, but I'm sure I didn't get it.