The block quote below is taken from this Toronto Star article. You can find the blog with images of all the pages here and a subreddit meant to keep tract of the conversation here.
At least 15 hidden messages have been discovered at the school’s D.B. Weldon Library, written entirely in symbols on standard printer paper, and concealed in plain-white envelopes tucked inside the pages of various books.
Each note is accompanied by an item, like a feather or a gem stone, that appears to relate to the symbols. On each note there is also an image of a household item like a vase or table.
“It’s completely baffling!” said assistant professor Mike Moffatt, who found one of the messages two weeks ago Sunday.
“I’d taken a book off the shelf on international economics,” he said. “Inside the book there was an envelope. I immediately thought somebody had been using it as a bookmark.”
“But when I opened it up, there were two items in it. One was a green plastic leaf, like something you’d buy at a dollar store, with two paint splotches on it. The other was this piece of paper covered in symbols with an image of a pillow,” he said.
Moffatt snapped a photo of the note with his smartphone and shared it on Twitter, hoping others had come across similar puzzles. He was not disappointed.
“People started saying they had found notes in the past as well,” he said. “Some had actually kept theirs, so over the last two weeks people have been coming forward.”
The economics professor has been keeping track of the cryptic messages on his blog, but despite an influx of attention, no one has been able to figure out what the cryptic notes mean or where they came from.
Moffatt said various cryptography enthusiasts have tried to the crack the code, performing frequency analysis (looking at how many times symbols appear) as well as various deciphers, but to no avail.