Is there a sure fire way to write a best seller?

You could always just money cheat away the added income if you don't want it and pretend they're making a higher donation somewhere. Or buy a few of the super expensive violins and keep them in your inventory which will make your bills higher taking away some of the future royalty income coming in. Once you no longer need them just resell them for less money or leave them lying around on a public lot somewhere.