This is the story of Roberto della Griva, a young Italian noble, and his travels around the world. As a teenager, Roberto took part in a siege, which radically changed his view of life. His father died in that siege, and later, Roberto decided to leave his father's lands and move elsewhere. He settled in Paris, with the elite intellectuals of that era (mid-17th century). The Parisian scene that Eco portrays is a very colorful one, with both fictional and true characters -- like Cardinal Richelieu, Cardinal Mazarin, and even a certain young man of 17 who was designing a computational machine at that time...
The story begins when Roberto, a sole refuge from shipwreck, finds himself on another ship. But this ship is strangely deserted, as if the crew fled from something horrid, leaving everything behind. Roberto's story is told by a scholar, presumably Eco himself, who investigates Roberto's carefully maintained journal. Slowly, as the story unfolds, we find more and more and Roberto's past, and later on, he slowly starts to find out more and more about himself.
Roberto is indeed in a most awkward situation: In an empty ship, a few hundred yards from shore, he cannot reach land alone. It seems like he is trapped. And to pass his time in his loneliness, he starts making up stories about his mysterious evil brother, Ferrante. It seems like deep inside, Roberto knows that Ferrante is nothing but a creature of his imagination, and yet, his actual life story is filled with gaps that cannot otherwise be explained.
And from the Worlds of Romance, Roberto moves to find refuge in philosophy. The science of these ages was not very advanced, and the heated debates at those time -- not long after Galileo's condemnation by the Inquisition -- are weather the Earth revolves around the sun, or is terra firma really firmly set; and also, is there Void in nature -- that is to say, can vacuum exist. The idea of life outside Earth is also pondered, with Selenian creatures -- the natives of Luna -- as the most likely candidates. Later on we find that Roberto is on a scientific mission himself, sent to seek a solution for a scientific problem of great practical importance. But Roberto's philosophy shifts from these “temporary” questions to those questions that bothered people from the dawn of time: What is life? Is there a God? And most of all, the question of Free Will.
There are several layers to the story: The story-telling scholar, who sometimes lets the story flow freely without interrupting for whole chapters -- and sometimes adds notes and interpretations; the story of Roberto, told by that scholar; Roberto's story, as he thinks it up; and also, Roberto's dreams. I think these layers mean a lot, and hint a lot, as their paths cross in strange ways; but I cannot say any more about this, for fear of spoiling your own discoveries. I will only tell that our scholar often makes notes regarding Roberto's story-telling capabilities, which more often than not are reflected back, seemingly unnoticed.
All in all, with the deep philosophical debates and Eco's superbly crafted prose, this is one of the best novels I've read to date; but it is extremely slow-moving, very much like Roberto's unmoving ship, and not an easy read.
In Eco's works on semiotics, he often discusses the question of the relationship between author and reader. In this book, Eco, as a writer, plays very nicely on this theme. More than once, he turns to the reader and discusses the advances of the plot, not as some all-powerful observer but clearly as the author. For example, near the end of Chapter 22 we find:
"So we may assume that gradually [...] Roberto was cured [...] (unless the reader chooses to insinuate that because from now on I need him on deck full-time, and finding no contradiction among his papers, I am freeing him from all illness, with authorial arrogance)."
Note that here, the distinction between the scholar that supposedly wrote this book, based on Roberto's notes, and the real author, that is, Umberto Eco, becomes totally blurred.
Eco further blurs the line between fiction and reality by including rather bold references to other works of fiction, including his own:
"For the captain it was obvious that the books, having belonged to a plague victim, were agents of infection. The plague is transmitted, as everyone knows, through venenific unguents, and he had read of people who died by wetting a finger with saliva as they leafed through works whose pages had in fact been smeared with a poison."
Could it be that the captain had read the notes of Adso of Melk, later published by some other scholar as The Name of the Rose?
The book is also filled with references to many other works, not only Eco's. From Six Walks in the Fictional Woods, for example, we know that Eco has a keen interest in Dumas' stories. And indeed, in The Island of the Day Before, we can find references to both The Three Musketeers and The Man in the Iron Mask. And there are many more; at times I thought that reading the book was a puzzle game, where the reader has to find all those hidden references and tributes.