A while ago I bought an invisible book. Or at least I think I did. It’s hard to tell. I certainly got a confirmation email from its author and creator, the artist Elisabeth Tonnard, advising me that it had been sent and acknowledging my payment of €0. This seems like a shrewd investment: my book is one of a limited edition of 100 (neither signed nor numbered) and, as Tonnard’s website says, it is ‘a product without a single fault, available at the lowest price possible’. To make the transaction a little more concrete I also ordered the set of (visible) postcards accompanying the work. Highlights in the History of ‘The Invisible Book’ includes pictures of the book’s early underwater testing in the Galapagos Islands, its acclaimed 1962 exhibition at the New York Public Library, and the undisclosed facility where the original manuscript has been kept since the 1870s, although ‘some say it is no longer there’.