Due to the length of time covered and the size limitations, this infographic is not complete; but it's still a good read. While it catches many of the important early steps in ebooks (like the Voyager Company's Expanded Books), it also leaves out one of the earliest ebook readers: the Sony Data Discman, which debuted in 1990. I think that ground-breaking device should have been included.
But leaving out an early ebook reader is relatively minor when you consider all of the history that has occurred since this infographic was released. Agency ebooks have come and gone; companies have failed, and the US ebook market has plateaued.
What do you think was the most significant digital publishing event in the past 4 years?