Amazon has gone to great lengths to make the e-book market what it is today. The first step was the introduction of a cheap e-reading device: The Kindle. This got the market started and from there, they introduced cheaper and cheaper models. Once there were enough e-readers on the market, more and more booksellers published e-books. Amazon has been trying to make books cheaper but has come against a lot of resistance from the big publishers. Regardless, they have been doing trials of two different book sale/rental models. Either of these two models could represent the future of e-books and publishing as a whole.
One scheme that tested recently is when an author is paid based on the number of pages read. This is the most controversial of the schemes. It means that when a reader loses interest and stop reading, the payment to the author stops there. This is extremely beneficial to readers who will only have to pay for the pages they read. The plan would specify different per-page rates for different books. This looks to be a non-starter for the major publishers and might be limited only to books published by Amazon.
The other scheme is the monthly flat rate model adopted by services like Netflix and other streaming services. In this scheme, a monthly fee is charged and the reader can read as many books as they want during that month. The authors would get paid a royalty every time a book is read.