the lack of page numbers is about the one thing I don't like about my Kindle.
I do miss being able to glance down at a book and physically seeing I'm about 1/2way through.
The other things mentioned ... A Kindle can still be read if you lose power. I have to plug mine in for a recharge about every 7 to 10 days.
What else I like
No dusting books. No moldy books in my basement. No trying to convince somebody to take all my used book "donations" off my hands because I desperately need space but can't stand to throw out a book. This was a pretty big deal in our house as my husband was developing sinus issues and his Doctor gave us a list of things to eliminate. Old carpeting and old books were big.
No remembering where I left a book or which shelf I left it on or whose bed it might be hiding under. My entire library is right there in one little gizmo. I carry over 1000 books with me and if I get bored with one, I just move on. Don't know what I might want to read while I'm on vacation? Doesn't matter because all my books plus the entire
Amazon store will be traveling in my purse.
Easily Searchable text ... Easy to find highlighted text
THE PRICE. I keep track of my book expenditures via my Shelfari account and I now spend about 25% of what I used to on books and I was a frequent user of 2nd hand stores, garage sales and book swap sites. I have such a list of under $3 to free books to read that I could probably stop buying books altogether and not run out of new material to read for 5 or 6 years.
The ability to simultaneously share books. In explanation, I buy a book once and my Mom, my neighbor and I can all read it at the same time on our Kindles. We don't have to take turns.
Easier on my eyes. Adjustable fonts and eInk screen. With my Kindle, I don't feel nearly as blind as I use to.
One Click. One Click. One Click. I can buy a book anytime at almost anywhere. I bought one on a Disney boat last week.
An eBook never has to go out of print. Think of how many books have been lost over the years because the author/publisher doesn't consider it profitable to keep the book on the market.
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as for the OP another reason why eBooks are replacing physical books is that it is fairly low cost means for a Publisher to get higher risk books onto the market because they don't have to print, ship, and convince retailers to inventory the book and the print run of an eBook is always exactly equal to demand.
There is a new business model of Publishing popping up where a book is offered ebook only and then only the most successful of those make it to print.