The novel's a little slow to get under way but, once it starts moving, it's absorbing stuff -- I found the pages turning happily. I have no way of knowing if the book's underpinning is valid or complete hokum, but certainly it convinced me for the purposes of the fiction. The translation, despite a few proofing errors (like "edging on" for "egging on"!), is generally the smooth ride you expect from Alberto Manguel. I had the odd sense when finishing the book that I'd at last got out of my mouth the bad taste -- which I'd not even realized was there -- left over from when, a couple of years back, I read (and detested) The Da Vinci Code as research for my parody Da Easter Bunny Code. At last I was reading a Leonardo da Vinci conspiracy-theory novel that I could enjoy as rattling good fun rather than be forcing myself to read.
(There's one irritating element near the end of the novel, when all the characters are implausibly slow to notice something that's patently obvious, but I forgave the book this.)