The Invisible Book of Invisibility was a textbook about the power of invisibility. The book is completely invisible, making it difficult to find and, presumably, to actually read or do anything with. Copies of the book can be found in Flourish and Blotts.
"I'm never stocking them again, never! It's been bedlam! I thought we'd seen the worst when we bought two hundred copies of the Invisible Book of Invisibility — cost a fortune, and we never found them."
The manager of Flourish and Blotts told Harry Potter in 1993 that, at some point in the past, the book store had ordered a stock of the book, only to have all two-hundred of them disappear, and no one was ever able to find them, costing the store a fortune. Only the stock of The Monster Book of Monsters was considered more troublesome.
Behind the scenes
The Invisible Book of Invisibility most probably teaches invisibility spells as well as theory, however it is not known how people are supposed to read the book, considering the invisibility.