Haha, those are good questions regarding retention and ebooks vs. paper books.
As far as retention, I think I do a lot better than I expected. I’m not sure how it works out so well. As I’m falling asleep (this figures into the next question) I tend to do weird things like skip several pages or even change the font size accidentally, which totally throws me off of my position in the book. However I tend to recall very well where I left off and find the location fairly easily. Even so, it’s pretty annoying, haha.
Because of that I really do prefer paper books in that I tend to put them down and have a distinct transition to sleep, meaning it’s hard to lose my spot or doubt my retention. I also notice and recall page numbers subconsciously so forgetting a book mark is no big deal anyway.
Unfortunately I need light to read a book, and that almost always causes me to stay awake longer. It’s a tough call. Paper books are better in nearly every way besides portability and the light factor. And of course the environment, too - I imagine I’ve saved a couple trees by now and the ebook seems bomb proof. Definitely capable of saving a few more in its lifetime.
So overall it seems like the ebook wins, especially at night. In the last several years I think I’ve read several dozen books on it and maybe close to a dozen paper books.
It's also, curiosly, easier for me to follow written instructions, compared to spoken (at work for example).