I can give you one good reason for the explosion of ebooks in the world -- the difficulty of writing a book is only a fraction of what it used to be.
It was really, really hard to write a book in the old days. Typing alone was a huge pain. I mean, misspell a word and you had to go back and whiteout the error and retype. A very time consuming process.
Typing my book into digital format has been an excruciating, slow and onerous process.
It was so much worse when it was a typewriter. (Heck, paper and copying costs alone could make you a starving writer.)
You thought long and hard before you started rewriting a manuscript. Sure, you could mark it up and cut it up physically, but eventually you had to type a readable version, and in so doing, you were more or less saying "This is it."
Or not. If not, you had yet another typing job to do.
So I truly believe that many people, while maybe inclined to write a book, found the physical process too demanding. Especially since the monetary rewards, then and now, were not great. Especially with the uncertainty that anyone would ever like it or even read it.
I'm not saying this is a good or bad thing -- just that it explains why there are so many more books now.
There are more writers because it's easier to be a writer.
1 day ago