I hadn’t been looking at eBooks lately until this new computer and the excellent Calibre reader prompted me to take them up again. I did have a Kobo reader, but as I reported in 2014 it finally died. Fortunately I had my books stored also on a “My Passport” portable hard drive. I have been loading them up to this computer: nearly 2000 so far!
There are so many sources of free eBooks. I am sure you have heard of Gutenberg, but there are some good local ones to check too, for example Free eBooks from University of Adelaide. There are amazing specialist, thoroughly up-to-date books and journals from the Australian National University Press.