At Swim, Two Birds

Has anyone ever read this?  I have to confess, I'd never even heard of it.  Brian O'Nolan, writing under the pseudonym Flann O'Brien... I found a copy in my parents' house, picked it up, was blown away by the first dozen pages but then had to go to sleep.  The enthusiastic cover blurbs by James Joyce, Dylan Thomas, Graham Greene, and John Updike, given the comic nature of the writing, I assumed were fake, in that Irish literary hoax kind of way.  But no... they are real.  How could I have never heard of this book, and even more puzzling:  what was it doing on my parents' bookshelves?