Amazon.com Inc. said Wednesday it will begin offering do-it-yourself authors and publishers a bigger cut of book sales on its Kindle e-reader – but with strings attached aimed at keeping prices down for consumers. The company said that starting in June, it will offer users of its e-book self-publishing program, the Kindle Digital Text Platform, royalties on book sales of 70 percent after delivery costs. With those costs equaling less than 6 cents per book, Amazon said authors will be able to earn $6.25 per copy on a book that sells for $8.99, rather than the old rate of $3.15. To qualify for the new rate, authors and publishers must meet several criteria. The book's list price must fall between $2.99 and $9.99 and be at least 20 percent below the lowest price of the physical edition of the book. It also has to sell on Amazon for the same price, or less, as it does with competing book sellers. Finally, it has to be available everywhere the author or publisher has intellectual property rights. Amazon said the new structure will not apply to books published before 1923 and will only be available for books sold in the US, initially.