I've often wondered why it should be so painful to see typos and errors in books. Really, it's easy to see what the intention was whether the error is spelling, grammatical or factual. One needn't be held up. Yet sometimes, it's [sic!] seems a tear in fabric of the universe has opened up.
Typos drive me to distraction. I recently read James Purdy's On Glory's Course, and the sheer number of mistakes was distressing. (My edition is a Penquin from 1985.) The slips ranged from one of the main character's name being misspelled at one point, to occasional words missing; it was perhaps the most error-filled book I've encountered, certainly on a per page basis (I remember Vollmann's 900+ page The Royal Family being replete with mistakes. Most of these I tended to ascribe, fairly or not, to a lack of editing in Vollmann's work--an assumption based on a combination of his famous refusal to budge on his books and their often incredible length. I even bothered to check certain pages of the paperback version to see if anything had been caught since the original release. Nothing I checked had changed. Also Penguin).
Each error I stumble across irritates me for just a moment, making me the tiniest bit angry, causing my mind to wander away from the text at hand as I almost try to will the thing away.
I was able to get over it for the Purdy. It's a wonderful book, as are all three of his that I've read thus far. If something intelligent occurs to me to say about it and/or him, it'll be in another post. I'm not holding my breath.
Slight irrelevant update: actually, it now occurs to me that the most typo-laden book I've ever read has to be Stan Goff's otherwise excellent Full Spectrum Disorder, published by Soft Skull Press.