In this alternate reality book, there are two kinds of people: those who can only remember what happened yesterday (Monos) and those who can remember what happened yesterday AND the day before yesterday (Duos). I found it to be a fascinating concept and one that had me thinking throughout the story. It's considered better to be a Duo simply because they can remember two days in the past instead of one. Sounds silly and arbitrary, but I think that's the point. The parallels to other forms of prejudice are clear. The Duos are thought to be smarter, they get better jobs (some jobs are off limits to Monos), and it's considered a "mixed" marriage (and not a good thing) when a Duo marries a Mono.
All of this is set in a more ordinary world where Mark, a Duo, is a best-selling author who is now running for Parliament. His wife Claire is a Mono. A woman's body is found not far from their home and policeman Hans, a Mono who pretends to be a Duo in order to keep his job, begins investigating. While this is essentially just another suspense novel, the added element of the memory issue really made it a great read. Everyone uses an "iDiary" (invented by Steve Jobs!) to record what happened during the day so that they can always look back. If they try hard enough, they can remember "facts" like when they married, how to cook, etc. They have a harder time remembering how they feel about someone or how that person made them feel. This was a good read and I loved the ending.
