How Do I Change the Font Size While in the Web Reader?

To change the font sizing in an eBook open in the Web Reader perform the following steps:

Click on the menu icon in the upper right of the navbar

Select the Tab with the Settings (Gear) icon

The font size controls can be adjusted by using the buttons on either side of the Font Size indicator. The button on the left decreases the font size and the button on the right increases the font size.

As font size is adjusted, the results are shown in the preview window.
After selecting the desired size, click "x" to return to the ebook.

New font sizing is applied