Depending on the display settings, Kindle for PC may not give you an optimum viewing area. Monitors that are in portrait position and Tablet PC’s can be troublesome viewers for reading via Kindle for PC because you are presented with a very narrow page to read. You can modify the page width by adjusting the Words Per Line setting.
1. Open Kindle for PC.
2. Go to the menu at the top and click the Aa button. Use the Words per Line slider control to adjust the width by sliding the control towards the max (right). When you have found the correct width, click anywhere outside of the menu box.
Your viewing area will now be much easier to use.
You go from something like this: