Assuming your laptop has hardware that has Linux support—wifi cards manufactured by certain companies are what typically make things difficult—a just works distribution like Ubuntu, Mint, and Pop!_OS will have a gentle learning curve for doing things that you want.
Mint is almost purpose made for people new to Linux or for people who just want to use their computer. It also has a large and friendly community around it, so there is community support, if you get stuck or confused on something. My parents, who are no tech people, have been happily using Mint for a couple of years now, with far less headache compared to Windows.
As others have said, the installation of whatever distribution you chose will probably be the most intimidating aspect of switching to Linux. It doesn't require being technically savy, just a willingness to learn and follow the procedures. It will be helpful to have your phone handy when you are doing the installation, so you can look things up incase there is something you don't understand.
If there is anything on the laptop that is important to you, back it up. The simplest way to install Linux will make whatever on the drive inaccessible. Additionally, find and record your Windows product key, just incase you want tk go back to Windows.
Assuming you have a Firefox derived browser installed, you could just add an EPUB extension to the browser.