I use Goodreads to keep track of the books I've read. You may notice on my Goodreads profile that I joined their 2018 Reading Challenge. This is the second year that I've done it, as it gives that extra bit of motivation to continue my reading habit:

I prefer to get my books from the library, but sometimes being able to immediately start reading a book I just found is great on Kindle. I also use the highlight function on Kindle, and receive a daily digest of recent highlights in my inbox, courtesy of Readwise.io. And of course, when I finish a book on Kindle, it automatically gets marked as read on Goodreads! That said, nothing beats holding a physical book in your hands.