What observation research might have been used in the redesign of the original kindle?

Amazon’s Kindle (its electronic book, magazine, and newspaper reader) has been far more successful than its SONY competitor. However, the original Kindle had some physical problems—button placement and page-turn speed among them. Correcting these problems resulted in the Kindle2, released in 2009 to glowing reviews. What observation research might have been used in the redesign of the original Kindle? (Refer Chapter-7/ Module-6)
Embed course material concepts, principles, and theories (which require supporting citations), along with two scholarly peer-reviewed references in support of your answer. Keep in mind that these scholarly references can be found in the Saudi Digital Library by conducting an advanced search specific to scholarly references.
Be sure to support your statements with logic and argument, citing all sources referenced.