This book lies at the epicenter of a triangle whose vertices are "The DaVinci Code", "Indiana Jones and the Last Crusade", and "The Magic Flute". I hasten to note that "The Last Cato" was written before Dan Brown's novel, so, when the narrator, Dr. Ottavio Salina, the famous paleographer, is recruited by her superiors at the Vatican to untangle a centuries-old religious conspiracy, and you say "this is just like Robert Langdon, the symbologist", remember that Asensi is not borrowing from Brown. Although I wouldn't at all be surprised to find out that Ms. Asensi saw the Indiana Jones movie! Don't buy this in expectation of bloody climaxes and killer Nazi/Opus Dei guys though. I cited Mozart for a reason.
I have a bias toward novels with elaborate scholarly puzzles in them, so when find out from a book jacket that the protagonists are going to decode Dante and track down the True Cross, I am full of anticipatory pleasure as we plunge into Codices and Byzantine history and archaeological digs. But ultimately I can't recommend the book. I'm willing to suspend a lot of disbelief for this kind of thing, but ultimately Ms. Asensi just asks too much.
I'm not even talking only about how vast in scope and flawless in execution this previously undetected age-old conspiracy has to be, or how they are supposed to get Universal Studios-style special effects with Graeco-Roman technology. I can grumble about that, but I can live with it if I have to.
But even more unbelievable is the social psychology of it all. Do you believe, for example, that it's possible to develop a series of physical and mental ordeals such that "those who pass them [are] incapable of doing gratuitous, senseless harm"? If that were so, wouldn't the Green Berets be going around doing good like Franciscan monks? It's not a problem for it if a character believes such things, but it gets to be a problem when the author does.
Throughout the book, people act like nobody would really act, both on an individual level and as collectives and institutions. I'm talking not only about the adventurer protagonists -- I'm talking about the Vatican itself, which supposedly wants them to find "the answer" and would rather they not die halfway through, but when it comes down to it is repeatedly content to send them off to hunt like so many ferrets sent down a badger hole and wait passively for their return.
At one point, for instance, the protagonists are stuck in what amounts to a hedge maze. Nobody has thought to bring in a cell phone, or a GPS locator, or a satellite photograph of the area. They could have. Nobody on the outside apparently feels like doing anything to make sure they aren't dead, like looking for them with a helicopter (they HAVE helicopters). For some reason, everybody is "sticking to the rules", as if Salina and company were out for a day of orienteering or something. And the whole book is like this. Of course we all realize that the author wants us to concentrate on the puzzles and challenges, and that it might be a poor piece of fiction if they just blasted through everything with rock drills and the Air Force and so on, but you have to have some plausible reason why people act as they do, don't you?
I know what has happened here, really - the author has gotten overly focused on the intellectual problems involved; she has worked hard to create a set of puzzles and she thinks that by doing so she has done all the work she really has to. But I disagree. Creating a novel is a puzzle of a different kind - somehow you have to put the pieces together in a way that makes the reader think that this sort of thing might really happen. (Leaving aside obvious fantastic/allegorical fiction, that is.) I don't think Ms. Asensi devoted nearly enough attention to this last step.