I can only think of three days of all of my touring where I was bored enough to want something like reading material to kill time. One of those days my touring partner was ill and needed a day of rest, and two days where the winds were so strong that I stayed put instead of working really hard to accomplish almost nothing. On those occasions I had some PDF files on my tablet that I could read but I also found other things to do.

I carried a 7 inch Android tablet on a couple tours, rarely used it and I did not have a smartphone on those tours. After getting an Android 5.5 inch smartphone, I quit carrying the tablet. I am old enough that my eyes do not focus at a close screen, I bought some very high power reading glasses (2.5 or 3.0) at Dollar Tree to allow me to focus on a small phone screen that was close to my eyes quite easily.

Raybo above mentioned downloading books from a library. My sister has a tablet that she downloads books onto from her local library, maybe it is a Kindle? She also has an Ipad, but uses the smaller tablet for books because battery life is much better. Thus, you may need to factor in battery life to your thinking.