IPad – Moving from Stanza to another eBook reader on the iPad Air

For years, I've been reading ebooks on my antique iPhone 4, using Calibre to painlessly send ebooks to it.

I have an iPad Air, and it just dawned on me (I guess I'm slow) that I oughtta be doing my reading on my iPad Air. Stanza's out of the question, obviously, but I like the effortless way Calibre maintains my vast library. I also like the ease with which Stanza works (though not the frequent crashes on the phone, obviously).

I'd be grateful if someone would recommend an eBook app which will continue to work with Calibre. I've tried over the years to replace Stanza with appalling results, and I'd rather not go through the agony of buying eBook readers only to throw my money away on disappointments (or worse, apps which make me rage). I'm a disabled vet and can't afford to go experimenting in things I can't use.

If you can tell me which app will work for me right out of the gate, I'll be a happy girl. These are my requirements:

1. Lets Calibre maintain my library and add books to/remove books from my eBook app's library;

2. Allows me to read ebooks easily.

3. (Optional) Allows to me change size and typeface of text easily, although this is an option I really, really want.