From my Amazon recommendations:
Can you spot the problem here?
What has happened is that I read hardback copies of each of these books when they were out last year. Both books were nominated for the Booker Prize I think. Now the paperbacks are out Amazon’s algorithm has worked out “someone who liked the hardback of X might like Y” but not “someone who read X in hardback probably doesn’t want to read the same book again”!
What I’ve done is gone in and rated both books again in the paperback versions, now Amazon will probably think I really, really like these books. (I did like them, but not enough to read either twice.)
[Incidentally the rerating of these paperbacks removed these two books from my recommendations and added in two new recommendations to replace them: one is a hardback that I've already read (and rated) in paperback, and one is a trilogy that I've already read (and rated) as three separate volumes. Not impressed!]