The line takes a bit of getting used to. The trick is not to use it to underline the text you're currently reading but to keep the line a good distance ahead of where you are in the text.
I'm not sure if white or black gradient would be better though.
If you want to experiment the source code is at https://github.com/rdwallis/MagicScrollWebReader
The line is an impossible challenge to design because the break between pages should be very obvious but also not distracting to the reader.