Every time Sam asked one of those questions or made one of those remarks about books it was presented as some sort of mockery of Dean's "smarts". Nor do I think Dean's answer to his question where he called someone else really say anything about his reading. Sam was being an ass even asking the question - as if Dean if didn't read it in a book, it was a "lesser" way to find out the answer, like calling someone who was more of an expert on the matter and actually discussing it with them is not as intelligent or as good as finding it in a book.
I remember back at that time, in Season 1, there was definitely some criticism of the presentation of that line because it was so ridiculous to act like Dean asking someone else who could give him the answer was a "stupider" option, because that is what Sam's implying when he doesn't believe Dean got the answer from a book by saying "What was the last book you even read?". Who cares how Dean got the answer, he got the answer, it's not less intelligent to ask someone who knows about these things than it is to go scrounging around books to look for the answer.