I remember being about 3 or 4 and my cousin (who's 12 years older than me) was reading a book and I scoffed and asked her how she could possibly read a book without any pictures, and I couldn't really ever imagine doing that and wasn't it really boring? She laughed and said I would one day, but I distinctly remember not really believing her because reading books without pictures was obviously silly.
I can't really recall books that weren't picture books having a massive effect on me with their illustrations. The Blake illustrations in Roald Dahl books were always great, and The Phantom Tollbooth's original illustrations were always something I loved. And Alice's Adventures in Wonderland, I think. I did want to be an illustrator for a while when I was much younger, maybe I should have pursued that. But it's hard and all. I have a friend doing a degree in "book arts" which is essentially that, and it sounds great!