slow performance and blurry text

I am currently using Adobe Digital Editions and trying to read a textbook for one of my classes. When I scroll it is extremely slow and I cannot scroll through pages smoothly. The words are blurry in one whole chapter and no matter what I do I can't get it fixed. Any advice on what I can do to make this work? I have been struggling to read this book for so long because of many issues with Adobe Digital Editions.