I agree that VC wasn't a great choice. But I don't see much evidence that they were reliant on investor money; per Crunchbase they only took $2.8m over 6 years of operation. And I don't think Amazon was their only potential source of revenue. Book publishers clearly still spend money on marketing, and Goodreads would be able to do very precise targeting. I also suspect they could have sold well-targeted ads to others, as some book categories strongly indicate monetizable non-book interest.