Choosing a reader with audio and what to do with the format?

Question

Electronic books

Don't throw sticks, I tried to find the answer myself, but...
I have a question. Tablet or Reader - I realized that the reader is because. the quality will be better, especially everyone writes about Kindle, but there are other questions:
1. Why are there no memory slots?
2. Is it possible to plug in headphones?
I always thought that reading and listening to neutral music was better for me. And my first reader (oysters readme 100) did everything I wrote about above.
Actually the essence of the topic:
1.
Advise a model for reading with E-Ink Pearl (as I understand it, it's cool and without it in any way) + with the ability to insert a memory card + headphones + charging from usb (powerbank)
2.
An additional question, there is a series of books that i want to read. In general, I found it already in all formats.
But in what format is it best and most convenient to read? There are no photographs in it or there are very few of them.
ps technical literature does not interest me

Answer 1

The reader is designed in such a way that the screen consumes very little.
That is why the reader (even with backlight) lives for weeks on a single charge.
In most readers, for the same reason, the processor is very weak. Rendering a book page once per second is not a problem. Decoding mp3, the higher quality - a decent load.
If you take a reader with audio and use audio, you will have to recharge every day, or even a couple of times a day.
Why then a reader, if you always have a smartphone at hand, which you still charge all the time.
Yes, there is kindle with audio, but it makes no sense for the above reasons.
Readers do not need additional memory mainly for the same reason - even 1 built-in gigabyte is enough for at least a year of reading.
The format doesn't matter. epub or FB2 as the most popular. It's just that FB2 is more popular, epub is more often seen as more commercial. There is practically no difference for the reader. Though plain txt.