This is the third volume in the "Cemetery of Lost Books" series, and it felt less like a proper novel and more like a prelude to the fourth book. There is no plot to speak of -- the mysterious event that precipitates the action simply leads to an extended flashback that fleshes out some details from the previous books and makes more explicit the connection between the two protagonists. Back in the present, a very short investigation leads to an abrupt and unsatisfactory conclusion, which presumably sets up the fourth novel. There's nonsense about a romantic subplot that's just an excuse for some machismo, and that's about it. And no, the icky situation from the end of the second book is not mentioned. (Perhaps it has not happened yet? Or is a delusion?)
The lack of story also means there is a lack of the atmosphere Ruiz Zafón is so good at. The characters, as usual, are likeable or interesting, but this was just a wisp of a book. I hope the promised fourth volume will bring this all together.