Jay Z david letterman glasses rapper jeans scarf

With the de rigueur black-rimmed "nerd" glasses and the casually-tied scarf, Jay-Z looks like nothing short of a best-selling author!

The serious rapper/hip-hop mogul threw peace signs on the way in to tape David Letterman last night.

But according to J's new biography Decoded his life has been anything but peaceful (until he met and eventually married Beyonce Knowles, of course). His 99 Problems started with being chased down by the cops as a crack dealer then on to the murders of his close pals Notorious B.I.G. and Tupac Shakur.

But all's well that ends well -- Jay ended up the most famous rapper of the decade with one of the most famous female singers as his wife ... life is good!