Some neccessary features for the Windows 10 version from the Microsoft Store
1. Enable the user to set the vertical scrolling as default. I know it has already been suggested but it really is the most annoying thing.
2. Enable reordering tabs of open documents with drag and drop horizontally along the toolbar.
3. Although right now it's blending well within the overall Windows 10 theme, an option to make the toolbar icons smaller would be useful - so the reading area could be larger.