LotR wins in the movie category but not in the book category. I tried to get through the Fellowship and holy hell was it boring. Tolkien could go on for pages about a single acorn hanging from a tree, it's annoying and makes me lose interest. It's like shopping with someone who wants to see every store, you just wish they'd make up their minds and stop stalling and lallygagging. Harry Potter books are fun to read and easily accessible yes, but they aren't that well written if you really pay attention.

Movies: LotR
Books: Harry Potter