Electric Literature reports a Nielsen survey, that suggests the rise of the e-book has slowed:
The fact that print is still the dominant format with 67% combined unite sales in 2014 seems to suggest that the market has roughly stabilized. That print books are would be the majority of the market was hardly a sure bet even a few years ago.
In his analysis Lincoln Michel argues that the concept of a format war may itself be mistaken, with different delivery mechanisms complementing one another as much as competing for market share. This is my personal experience, though I'd be the first to admit I am atypical. In most arenas.
