Concept of turning everything upside down - Arabia as superpower, Christian terrorists, and so on - was interesting enough, and was probably meant to shake our assumptions and prejudices regarding 9/11, Islam extremism, etc... except it was a few hundred pages too long. 
 On the pop fiction front, the plot was draggy and I had to force myself to complete the book. As for the literary side, I enjoyed the brief but very occasional insights into the main characters' lives (e.g. Amal's family background) which disappeared as the book went on. Otherwise, most of the characters were flat, including the villains. The details of the alternate reality became wearisome, especially if I got the references to the real world, and if I didn't, I got lost in the large cast of characters and geography and timeline. (The scene at the start of the book with the Travis crusader - there was no mention of when that occurred. I thought it was the same time as their 11/9 and was rather confused for quite a while.) 
 Other gripes: Some other reviewer mentioned that the Library of Alexandria was gimmicky and I agree. The whole book felt like: "let's see how rich and detailed an alternate reality I can describe in the book" (without the accompanying plot or characterisation) and that Library a convenient way of inserting more details. 
 The ending of the book was a let-down as well. Dropping hints about solving the mirage throughout the book, (view spoiler)[ then attributing it to a supernatural jinn, seemed like such a cop-out. I'm okay with the supernatural in the book - not everything has to be "science" or even explained - but it didn't fit with the tone of the rest of the book, which was (scientific) investigative. Even the supernatural/jinn thing wasn't properly dealt with. There was a dramatic ending with the sandstorm and the battle at Hussein's house (which did not leave me at the edge of my seat), and the author conveniently fails to address any of the readers' questions (perhaps hoping that the action would distract his readers?) The aftermath and implications were things I'd like to have seen brought up but nope - perhaps the author never intended to discuss them. (hide spoiler)] 
 In an interview, the author did say that "the story [he] wanted to tell wasn't about the Arab democracy that might have been, or that may yet be; it was about the democracy Americans were promised as an enticement for invading Iraq - the one that was going to spring forth magically from the ashes of Saddam's empire, without any regard for historical context". Would have liked to see slightly more explicit discussion on this, because if there were in the book, I've missed it.