Have you ever eagerly downloaded an eBook only to find that it's a hideously formatted mess that irritates you at every page turn? Of course you have (especially if you favour free or cheap eBooks). This video explains why those insults to typesetting occur.
The problem boils down to the choice of algorithm that's used to render the text. While fancy software exists to set the type beautifully, your Kindle favours a lazy layout in order to save resources. In other words, a Kindle's typesetting is kind to its battery — but not, necessarily, your eyes. [Computerphile]