I've no idea if I'm an average reader, but I read all sorts: SF, Fantasy, Crime, Biographies, Romance... The odd typo is forgiveable (my fingers often type form when I meant from) and understandable. I hate to see them in my own work, and I'm not that upset to see a few in an other author's book. But when the 'few' gets to be 'more than a few', and then 'quite a few', I lose interest in the book itself. I can't believe a writer would deliberately put out shoddy spelling over and over again, even if they felt by writing a busload of books with mistakes they'll get by, because the production process can be overlooked in the name of quantity. Give me quality any day. It's downright laziness to put out a book that is rife with typos. They are unwitting errors, and easily dealt with - most word-processing programmes pick them up (forgiveable and programmes are both highlighted in this post, because spell-check is set to google's standard) and yes, they won't pick up 'form', when I meant 'from'. I pick those up myself, by careful reading - I read the book backwards so I don't get involved in the story and it's kinda easy. And yet, I'll still miss a few and an editor/copywriter will pick those up for me. Every writer is judged by their work, and I want to put the best out. Every time.