Wikipedia
Bookerly
Bookerly is a serif typeface designed by Dalton Maag as an exclusive font for reading on Amazon's Kindle devices. Combined with a new typesetting engine, Amazon.com asserts that the font helps the user "read faster with less eyestrain."
Bookerly replaces Caecilia as the default font for the 2015 Kindle Paperwhite (3rd generation) and it will be used as the default font on Amazon's future e-readers. The Bookerly font was added to many of the older Kindle devices via firmware updates.