I am very happily using Moon+ Reader Pro on my 5" and 8" Samsung Notes. I just purchased a 21.5" tablet. (If my 5" phone is a phablet what does that make my 21" tablet?)
I just bought an HP Slate 21 Pro with Android 4.3 and decided to see how it performed for reading books. BTW no I can't hold it in one hand - it weighs a ton!

I cannot get either the Moon Reader basic or Pro version to work. They both appear to install successfully. Whether I try and open a book directly from within Moon Reader or I try and open it from Calibre Companion I get the same result. The screen flashes black, looks like it is going to open it and then doesn't - it just goes back to where it came from i.e. Calibre Companion or the Moon Reader bookshelf depending on where I initiated the open from.
I tried both Moon Reader versions, I tried uninstalling and reinstalling it. Nothing has made any difference. Is there a problem with Android on an HP device? Can anyone think of anything else to try? At the moment I am completely stuck........Jackie