I read a lot. Contemporary authors and older ones too. For the much older, one great thing is that many of their work is now in the public domain, aka they can be downloaded and read for free.
I often get them from The Project Gutenberg. But I always do some cleaning, a few edits and add my own cover.
I like doing my own covers. I find too many commercial covers hard to read on smaller screens, or they will be plain dull. More often than not, public domain books won't have a cover to begin with.
I like to adapt page layout for the screen, be it on an e-reader, a tablet or a computer (I do not read on my phone).
Depending on the book, I will rather read an epub/mobi or a PDF. In either case, I will make sure there is a working table of content, too.
My covers are often minimalist. Although most of them are very brightly colored, they should be readable on B&W e-ink screens too:
The epub is a standard epub 3.0, I made in LibreOffice Writer.
The PDF has been optimized for screen reading not for printing. It has been exported from LibreOffice Writer. The font used for the title and for the text body is 'Baskervald ADF Std'. I like it a lot and often use it.
I made the cover in Inkscape.
I have no idea if anyone beside me will ever need it, but here is the first one of what could become a recurring series of public domain ebooks: "Thirty Strange Stories, by H. G. Wells. In PDF and epub.
Happy reading ;)