I really loved the first half of the book. It was such a fun reading experience, discovering the mythos of Cordova, his body of work, and the few bits of personal history that the protagonist had access to. I wondered if the app might be too gimmicky, but I loved the extra layer of suspense as I scanned the symbol. What was it about to reveal? Sometimes I was afraid to look... 
 ...though it didn't quite pay off, either with the extra media or the story itself. I'm a horror reader and had a secret hope that this was going to be a horror novel, but it was really more a commercial thriller. And I totally don't mean that in a bad way. I just found myself wishing it were different. I was hoping for the next incarnation of House of Leaves (though that disappointed me in a different way). 
 Still, the potential. So exciting. On the basis of that, I'll boost this to four stars. 
 (Also, all the complaints about the italics in the other reviews are cracking me up. I didn't even notice!)