Impossibly slow, jumpy, startling scrolling, on Adobe Digital Edition Reader

Hello, I recently downloaded a textbook onto Adobe Digital Reader, and it is impossibly slow to scroll... it startles, it jumps around.  It’s truly frustrating. When I reduced it to a whole page, the font is too small to be comfortable to read.  I’m truly stunned at how badly this is working. I will never ever, buy a textbook this way again if it requires me to use this a a platform.  I find it ridiculous that it is far easier to read something online, than downloaded to my computer? No other application I use, gives me this type of trouble.