I want to buy my dad a good book for his birthday and not sure what to get as it's not my favourite genre I'm not widely read in it 
He has read and enjoyed all the Shardlake series, so something similar, perhaps with a historical bent (but not too similar) would be ideal. He also liked the Robert Galbraith, but I would say prefers the more mystery type of crime novel than the horror/gory kind.
He's read all Agatha Christie/Conan Doyle/Chesterton.
Has to be well-written.
All suggestions welcome, many thanks in advance.