I've been reading bits and pieces of this book for month and it was only in the last couple of days that I gathered the energy to finish it all. Let me state the positives of this book succinctly: it starts off excellently, the language is just hard enough but not too hard and the worldbuilding is fascinating. However, considering this is rated just below The Lord of the Rings and The Hobbit as one of the greatest fantasy-sci/fi works of all, I cannot quite see why. I believe that, perhaps, the language is more deceptive than it may appear - because precious little actually takes place within the work in terms of plot narrative.
When the narrative can be summed down to: assassin is kicked out of guild and sets off to explore the earth, then you have a narrative which isn't overly complex. Sure, things happen to our torturer, Severian, but at the same time very little also happens to him. Everything becomes a cycle of: kill new people, find new wonders of the world, sleep with a new girlfriend, rinse, lather, repeat. It's inane in its repetition and the repetition almost made me give this three stars.
But that said, the language is beautifully deceptive, and it was for this reason that I kept that extra star. The language is beautiful enough to distract from the fact that very little actually happens within the novel - very little of any kind of moral or significant depth, that is. Also, the worldbuilding was magnificently set in an Earth that was now Urth - a million odd years into the future, where technology and magic have become almost one and the same. I appreciated that aspect of creating another world setting for the book.
Yet, my overall summary is: only read this if you have a desire to complete a list of must-read fantasy books. The language can prove to be a stumbling block to some and aside from the language I could not find any real thematic or moral lessons within the book, which make it a shallow read and not so much of a deep philosophical read for once. But then again, as I said recently, not being able to find such things could also mean that I am not reading the book deeply. Or else, that I felt it was a novel in which I did not need to look overly deeply - being distracted by the language and world as I was.