Why Is Nicka little disapointed with Gatsby?

Nick is trying to figure out who Gatsby really is. Nick hears these rumors about gatsby, how he was a German spy, a murderer, etc.. Nick is disappointed with Gatsby because Gatsby has little too say. Nick wants Gatsby to tell him who he really is, what he does, where is he from. Unsurprisingly, Gatsby does not tell him, even though they talk a lot.