E-book subscription service Oyster just fattened up its catalog. After raising a total of $17 million to bring the Netflix model to e-books, Oyster is taking a moment to bask in its early success: the startup just surpassed half a million titles and managed to win over new deals with publishing behemoths HarperCollins, Chronicle, and Wiley. Oyster’s promise is simple: “read unlimited books, anytime, anywhere.”