Umberto Eco's The Island of the Day Before is a difficult book to review. Since finishing it last night I've been trying to figure out even what I would say, what words I would use to describe my reaction to it. It never grabbed me the way The Name of the Rose or Foucault's Pendulum did, but I didn't really dislike it (as I did Baudolino). Certain elements of the story were interesting (the search for accurate measurement of longitude at sea, the whole marooned on a boat within sight of land motif), and I really enjoyed the little old man who spoke in a variety of different languages at once. There are several very funny passages (I can't remember ever laughing out loud with Eco before).
On the other hand, I read through the entire book thinking that surely something would happen soon, that there was some missing element that would make itself known and make the book pop like some of Eco's others have for me. And that never happened.
Eco explores philosophical and historical issues in intriguing ways in all of his books, making all of them well worth the reading.