'The Cat in the Hat', because it was, as an adult, my first experience of one of these books. We received a copy of this book from the US one Xmas and, of course, I read it to my children, who absolutely adored it for all sorts of reasons.
These books were not, at the time, very common nor read in Ireland, and thus our lack of familiarity.
Now that same story has passed down to our last child and is lying in wait for a grandchild, more as a memento of their parent's childhood. What fun, what joy was created from the writer's mind, never to go out of fashion nor style.