Yesterday is set in an alternate reality where the population is split between Monos and Duos. The difference? A Duo can remember two days and a Mono only one. This creates a class divide and Felicia Yap uses it to explore prejudice.

At the heart of the story is a dead woman, assumed murdered however murder is pretty rare as most people don’t have the same grudges they would if they remembered everything clearly. However, the victim could remember everything, and had been institutionalised because of it. Her diaries suggest she hadn’t the only one either, all condemned to madness.

With no long term memory you would expect civilisation to collapse. To get round this, everyone keeps a diary, once kept on paper but now, thanks to Steve Jobs, people can store them electronically. If they study their diary regularly, they can commit facts to long-term memory. Also, children can remember everything, with memory loss starting at age 18 for Monos and 23 for Duos. This gap strengthens the stereotype of Monos being stupid, as it prohibits a university education. Just as in our world, the working class have greater hurdles to catch up with the middle class, who have better opportunities afforded to them by wealth and connections.

It’s a shame the lack of intelligence of a few reinforces the bigotry against the many.

It works if you don’t think too hard about it all. With the memory constraints, it’s a miracle this alternate world has the same technological advancement. I liked how precious the diaries were, a nod to current concerns over data privacy, as well as the potential for data loss. Claire discovers she is missing a period of time in her old diaries, events she didn’t attempt to memorise. They put trust in their diaries just as we trust in hard drives and cloud storage.

It seems to me that thrillers these days must have unlikable characters, and Sophia and Mark definitely fit the bill. Sophia is the victim, whose diary tells us of her thirst for revenge against Mark, a famous writer (books are written to be read over a couple of days at most). Her reasons for revenge are not revealed immediately, which helps keep the pace.

Fortunately for me, Hans the detective and mark’s wife Claire, are much more sympathetic characters. It says a lot that these are the Monos, whilst the Duos come across as arrogant and prejudiced. Normally, Monos’ career prospects would be limited by their status but Hans has been pretending to be a Duo, his track record at solving crimes within a day contributing to his success, both as a detective and as a Mono in hiding.

It’s the sum total of minuscule remembered gestures that makes love powerful. It’s the agglomeration of tiny recollected grievances that makes hatred.

Everyone assumes Claire was just the pretty but stupid Mono wife. Mark’s running for MP and part of his campaign is about mixed marriages, of which his is one. Yet there’s more to Claire than meets the eye. The change in her diary style over 20 years shows she has improved her writing skills.

The diaries provide much of the narrative, jumping around in time as well as between characters. There are also press clippings that add some context as well as shedding light on the mystery, or confusing it more in some cases.

It’s an interesting concept and I’d recommend to anyone who is getting a little fatigued by the usual domestic thrillers.

Yesterday is published by Wildfire, an imprint of Headline, and will be available in hardback and ebook editions from 10th August 2017. Thanks go to the publisher for providing a copy for review via NetGalley.

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Disclosure: I received a copy of this book free of charge for review purposes only. Receipt of a book does not guarantee a review or endorsement. My reviews are my honest opinion and are not biased for the purpose of personal gain.