I'd say the ebook writers should say in the directions that if you squint, that you should change your desktop to a lower resolution so everything is bigger. There's no reason to do that to your eyes if you are having a problem.

Then I'd say they need to teach you the steps of

Move some windows so you can see a blank part of your desktop.

In the blank part of the desktop, right click and choose properties.

Then choose the settings tab.

Then change the numbers on your screen area by sliding the slider to the left.

Then choose OK and follow the directions to check if your window looks alright.

After your window looks good, re-start the ebook and read in comfort.