I have an azw3 as described above. It can be converted into epub, using the extension from Calibre "Kindle Unpack", but there are no paragraphs, meaning that the all the words in the txt file is structured like a wall of text. I use SumatraPDF which can read all the azw3, mobi, pdf and epub2 and/or epub3 files with much less effort than Adobe Reader.
Edit: Oh, I forgot to tell you. The azw3 file can also be unpacked into xhtml files.