"Eco's writing is so infectious, lively, and likeable that I thought it appropriate to pen my review in his style.

1. In which I, as reader, feel used.
Yes, I'm almost certain Eco wrote this thing for the sole purpose of informing us of how knowledgeable he is of the finer points of monastic orders, book trivia, and medieval philosophy.
Knowing most would not put up with this crap for 500 pages, he wisely chose to interrupt his many digressions on poverty, heretics, whether or not Jesus laughed, Aristotle, architecture, etc, with an amateurish mystery plot. It's pedantry disguised as fiction. I've been used.

2. In which the pace sucks.
Just when you thought it was getting interesting, just when the plot is getting meatier and it grabs your attention, here comes a dissertation or a long drawn description of doors, churches, parchments, beasts, characters that are totally irrelevant to the plot, and backstories that do nothing to shed light on the events. You must often wait a chapter or two to get back to the mystery that drove you to read this thing in the first place. Do yourself a favor and quit after he has solved his first "mystery" (page 25?).

3. In which its heavy-handedness is offensive.
Lurk around bookworms long enough and you're bound to find some pompous pseudo intellectual enraptured by the rich, textured, yet subtle literary clues so artfully crafted into this piece: "You mean to tell me that Jorge De Burgos, the blind monk, is actually a nod to Jorge Luis Borges, the blind Argentinian writer? Whaaat?" So clever...
I'm sure the late Borges heard this, face-palmed, and then turned in his grave.
EDIT: I have been duly informed, perhaps by the type referenced above, that Borges was actually alive when this "work" was published. He died shortly thereafter...

4. In which the plot fails to deliver.
Provided you made it as far as the end, all in hopes of finding a conclusion so stellar as to redeem the drudgery that preceded it, what one is most likely to find is disappointment. Most, by the time they get there, will already know who the culprit is, and given the setting and the tools the protagonists are carrying, what will happen in the final scene.
Is it a fantastic twist? A conspiracy centuries in the making? No. Just lunatic ravings akin to the ones that drove Eco to romanticize about love, lust, knowledge, etc..."