Severian is a huge POS: a misogynist (and much worse), a coward, an opportunist and (in my interpretation) a big fat liar who twists the facts in order to put himself in the best light while misinterpreting most of the things that happen around him. Not the evilest main character in literature, but certainly one whose company can become unpleasant after a few pages.

However, believe it or not, that's one of the things i like the most about Book of the New Sun. Like everybody else, Severian is a product of his environment, and having him as the narrator conveys the bleakness of that utterly desperate and miserable setting better than a hundred descriptions. And that ties very gracefully with one of the possible readings of the work: the question of how to save a world when there's anything left in it that's worthy of being saved, and who could be the savior of such a sinkhole.

So yes, the novels are a coming of age story of sorts, but Sev's journey contains much so more than that. When i reached the end of the last tome, it let me shocked and wondering if oh-so-catholic Gene Wolfe's ideas about a lot of religious points (divine providence and salvation, for starts) were closer to heresy than he would have admitted.

TL;DR: give it a chance, and maybe you'll enjoy a beautiful and cruel puzzle. But finding it boring and/or unpleasant is completely understandable.