I've never heard of an author who doesn't read ANY books EVER, so I call preemptive straw-man on that.
However, if I honestly saw someone say that, instead of thinking, "I won't buy their book," I'd think, "I wonder why they don't."
For instance, I bought a book last year written by an author who -- I'll bet -- has not read very many books! The book was "
I am Nujood, Age 10, Divorced" and it was a biography by a young, poor girl in Yemen who was married at age 10 and had the courage to demand a divorce from the authorities.
Her book was written with the help of another author, of course, if only because I think Nujood probably doesn't speak English fluently, but I have no idea (and don't really care) how much of the narration was Nujood's and how much was her aid's. The story is wonderful and touching and I don't care how many books either of them has read. Nor would I expect Nujood to have read many books at all in her short life so far, but that doesn't mean she doesn't have an incredible true story to tell.
So, having said that, IF there was a hypothetical author who didn't read books, I'd merely wonder why, but I wouldn't write their book off as an "oh, I obviously won't read THAT." Then again, I try not to make snap decisions about people based on something they wrote on an internet forum.