It is definitely interesting. Its one of those books that leaves you feeling a bit dumb, as so much seems to be going over your head. At the end Hildegrin reappears, and we meet Cumaean, but rather than me going oh those guys, I had to flick back I admit. And of course Hildegrin was there at the beginning with Voladus, and ferried Severian across the lake, and there we saw the cave of Cumaean, and it was discussed that the botanical gardens were built for her. The whole book is a complete head fuck! And definitely needs to be reread once I get to the end of volume 4, just to try and make sense of all it all. Its all rather epic with a very complex mythology, which actually reminds me to an extent of Sandman by Neil Gaiman. I did enjoy the tale within a tale which of course was a retelling of Theseus and the Minotaur's labyrinth, and was totally confused by the play within the story.
And yes Severian is totally dis-likeable, but then many protagonists are. Who actually likes Rand Al Thor for example? And poor Jolanta, never has a female character been treated so badly.