While bardsandsages may have made a good point regarding how one talks past a bouncer and enters a building, I'm not sure it works for how one markets a book deal. The game splits social skills up into "Bluff," "Intimidate," "Diplomacy" and "Sense Motive" for a reason: there are a lot of different things one can do with conversation, and players, for the most part, are familiar with the nuances of how to hold a conversation. For opposite reasons, there's only one "Profession: Literary Agent."
And if the DM needs to have the player give him cues on what's going on for the DM to resolve the situation, and the player is angry because roleplaying out the marketing of a book deal is 1) not why they got into D&D at ALL, and 2) something they have no clue how to do in real life, then perhaps everyone needs to step back and ask why the plot centers around marketing contracts.
I'd suggest that perhaps this is the DM's fault because he's the one who's most in charge of the plotline, but I know that then everyone who's been ranting about how its not the DM's job to serve the players and the DM has the right to do this and that and the other thing, will instantly switch positions. And I'd hate to see that, really, I would.