Youngblood Hawke; by Herman Wouk.

A young man full of vigour in more than one way, of mind and body and creative facility, shot to fame with his first book published and for good reason, and he has not only more ideas but elaborate plans of many many books he sets out to write. But he is innocent in ways of the world and learns at a cost to his health and creativity, to his heart and to his whole being.

The publisher, the agent, the high society that takes him up including the wealthy married woman who has him in her sights and soon in her claws, and he is an observer of the whole process as much as a pawn and a player learning to do better.

Very moving about the protagonist and very educating about the world out to devour him.