Into the Wardrobe

Hello! I have been assigned an essay on an author that changed society. I picked C.S Lewis, because I loved the Narnia books, but I need to justify my picking him. I know that he had an impact on society, and I sort of realize what it is, but I can't seem to be able to write it out and explain it. So, I was wondering if anyone could steer me in a general direction of a website that could help get my thoughts into some kind of order, so I can explain it properly.

Also, sorry if this kind of thing has been posted before. I've looked over the first few pages, but haven't found anything.

Again, any help would be much appreciated!