Amazon’s Kindle Unlimited product offers readers an all-you-can-eat model for book subscriptions. The books are mainly self-published titles (and Amazon pays authors by the number of pages read). The model sounds great in theory—readers download books risk-free, encouraging discovery of new books. But since Amazon counts how far into a book devices sync to calculate payments, tricks like filling up documents with extra nonsense pages and getting users to click to the end of the books means scammers are collecting big payouts while squeezing out more legitimate authors.