I read Johnathan Strange and Mr Norrell about 16 years ago and I loved it at the time. Piranesi was published last year and I've just had a chance to listen to the audiobook. It's fairly short and well read by Chiwetel Ejiofo.
Piranesi is a magical and mysterious book that reminded me of the Narnia tales of CS Lewis. It's a story about a massive house, deserted and partially flooded, filled with strange things and inhabited by the narrator and another.
The story flows and was succinct and well constructed. I totally recommend it.