(a late reply, I know)
Thank you - finding your post led me to installing this app on my "ancient" (Android 4.2) e-reader. I've had issues with re-installing the paid version of Calibre Companion after a device reset. The CC demo version works flawlessly.
It may be because I'm on an 8" e-reader that the accept/decline buttons are on the bottom of the page - I didn't have to scroll to click the button. It's clear that the app isn't designed for e-ink screens but it is functional. Icons are a tad small/low contrast but with time I will get used to where they are/what they do.
Perhaps you could email the developer (support@kpwsite.com)?
I can sort by book series on my device! These books are grouped into folders (hallelujah!) then individual books are listed below. I will miss connecting to Calibre as a wireless device (not the content server). I can happily live with this limitation because book series folders! I have to say after testing the basic version for less than ten minutes, I upgraded to the paid version because want to support this developer.