I watched it on Sky the other day. The whole number 23 thing is, I suppose, the modern equivalent of a MacGuffin: it gives a reason for the central character to do what he does, yet it's not actually important in itself. It would be just as good (or bad) with a different plot device - the book, rather than all the numerological mumbo-jumbo, is what drives the plot.
Yes, it is very silly.