I take my Kindle Keyboard with me almost everywhere.
I did read news and books on Palm devices many years ago, including the Z22, which probably has a smaller screen than any currently marketed smart phone.
I will only read a book on my Fire HD if it is a library borrow that isn't available in Kindle format (such as if from the Brooklyn Public Library Cloud Library, formerly 3M).
I notice that paper books aren't among the choices. I do still read them as well