Text in E-Book not readable

Hi everyone, 

I am experiencing an issue with the E-Book that I opened in Digital Editions.
The text in the Table of Contents is readable (sharp) and the content of the book is not. I want to make it sharp and don't know if and how that works.

I checked the "Adjust Clear Type" settings in Windows but there is nothing I can do to improve it.
I also adjusted the Text size, unfortunately with no positive result.

The Helpcenter from Adobe directed me to you, so y'all are my last hope 🙂
Q: Is there a way to convert it to PDF and open it in Acrobat to read it? This was their suggestion but we didn't know if and how that works.

Thank you in advance for your answers!