My snarky reply above notwithstanding, I kind of agree with Wolf. I've always tried to keep the number of books on my Kindle down to about 20 or 30. Lately I've gotten sloppy and I have close to 50 books on it and it's getting harder to find what I want. I'll clean it up soon.
On my phone I keep more books because I have a 128gb micro SD card and I use Moon+ most of the time and it makes it a lot easier to scroll through the books to find the one I'm looking for. Also if I forget what a book is about, which I'm more likely to do when there are more books, Moon+ makes it faster and easier to find out.
This is a good example of what competition can do to ereading devices if there was competition. Moon+ has to compete as an app so it's excellent, as are most of the other ereading apps. The Kindle doesn't really have to compete as a device since the competing is done in the book store. The Kindle is, to my mind, the best reading device but it pales in comparison to most ereading apps in terms of features and the quality of those features.
I realize I'm shaking my fist at a thunderstorm but it kind of feels good so I'm doing it.
Barry