During my mother's childhood, her mother used to hide from her children by reading the dictionary in the bathroom. If I remember the story correctly, she also read a full set of encyclopedias while there. Either would have taken her years since nine (9) individuals shared one bathroom. (My grandmother's people didn't believe in higher education for girls.Not uncommon practice at the time. The pity is, she was an actual genius and was always frustrated by not being able to continue improving her mind.)
When Santa was young, his mother bought a set of World Book encyclopedias for him. Santa was already a really smart kid and read widely. He read each volume as they purchased it.
My own father read both the World Book and the Encyclopedia Britannica over the course of several years - in the time he waited for us to finish breakfast and head to the school bus.
There is even someone who has read the Encyclopedia Britannica and written a book about it. A.J. Jacobs did it in one year and did it to recover some of his under used brain capacity. It is a sweet, self-depreciating book about his adventure.
His goal was to retain the knowledge he accumulated while going through all of the volumes. And, from the sound of things, he has done just that. Okay, maybe not completely, but he has retained far more than I ever would have.
Me? Based on my bookshelves, I should be rival to either my grandmother of Mr. Jacobs for smarts. My father, well, him I never felt I could compete with.
I do own a large, dated, collection of World Books and the following year books. A set of Popular Science books - projects, I think. Several dictionaries are spread around the house, but not always for knowledge based reasons.
In my bedroom I use one a rather large dictionary, not to read, to get added lift when I climb into bed. It is a little high for me and it makes life easier. I even had a spare five-incher in my guest room in the event a vertically challenged person stays the night. The one in my office is used to prop up my laptop so it is a more comfortable height to work.
Will I ever aim that high?
I wouldn't want to be the know-it-all in my family and have basis to support the claim.