Thanks!
I looked for a Calibre app last night but couldn't find it. I saw a few apps that appeared to be utilities for Calibre but didn't really know what they were.
Somehow I managed to get Moon+ to open one of the free epub books i downloaded today, though i don't remember how i did it. (Yes this is an appropriate time to wonder how someone so hopeless with hardware and apps could ever do software programming. I can't explain it.
) So I guess I will use Moon+ as my ereader, at least for now. I still have some Kindle books to read, so I'll use the Kindle app for that. For future non-technical books I might use Nook just because I'm still annoyed at Amazon.
Re: the Nook version of the long book I plan to buy, I looked at a sample on the Barnes and Noble site, where I saw the layout problem. Then I looked at an ebook sample on the publisher's site, and it was fine. If I buy from the publisher (O'Reilly ), I get it in several formats and they will update my copy when they make corrections. As near as I can tell, if I buy a Nook book from B&N I don't get any updates and if i don't like it then I'm SOL. So it seems worthwhile to buy from the publisher.
For my next trick, I need to open a Dropbox account. Let's hope that at least will be easy.