My Sim completed the specialist writer challenge with romance novels before I read your guide. I didn't know there was such a thing as a masterpiece before that so he had already written 12 romance novels! However, it seems for masterpieces it's different in that you don't need to surpass your previous genre, only match it, to become Master of the Masterpiece. He just reached it with 12 (unless I didn't pay attention and notice earlier) and it says:
Masters of the Masterpiece are incredible craftsmen that perfectly tell every story they want to tell. Their masterpieces rarely fail to become hits or best-sellers.
The last few books he wrote were masterpiece bestsellers that give over $20,000 in royalties per week! Stacked together, after writing a few books each vacation, my Sim family never needs to work when they are in Sunset Valley (he is a superstar rock star, so he doesn't have to go to work anyway).
