Roberto, only survivor from a shipwreck, finds himself on another ship.  All alone again.  The ship is only a few hundred meters away from a tropical island, but the distance is too large to bridge by Roberto alone.  For the time being Roberto can survive on the ship's supplies, but they will not last forever.
While wandering through the ship and its many rooms and corners, Roberto finds both a huge collection of clocks, and a variation of plants and animals.  But no evidence at all of human presence.  Throughout his days, Roberto reflects on his life, from the war he was involved in as a teenager, via his experiences in a "modern city" like Paris in the middle of the 17th century.

The story is told by someone going over the annotations of Roberto.  He tells about Roberto, or simply quotes him, and sometimes it seems as if Eco is telling about the scholar telling about Roberto.  And sometimes it's not clear at all.  Who cares?  This mixture is great as it is.  Throughout the story we discover Roberto's past, and during that discovery we discover the blending of facts and his imagination.  And that leaves us with some questions, as some parts of his imaginative life does have evidence of reality.

Not the easiest story to read, you cannot go over this like what we call in Dutch a "station-novel", you have to keep your mind at it.  But when you do that, I think you'll discover one of the best novels written in modern time.  "The name of the Rose" was extremely good in my humble opinion, this one was a few degrees better.