I am just looking for a reader on the Mac. No plans for getting a reader.
Both the B&N "nook" and the Amazon "Kindle" make competent ereader software for Mac/PC. Both require some amount of "account setup." The Kindle version I believe requires credit card info. The Nook version I think does not. Neither is particularly "tied" to the hardware ebook reader that each company sells, name aside. The Apple software tends to be more onerous, in terms of how "tied" their software is, IMHO. Kindle is oriented towards MOBI files, Nook is oriented towards EPUB files. Suggest you set aside your fears about having to set up an account long enough to check out the software and see if either of them actually "works" for you or not. And/or compare to the Apple software, again if you can set aside your "account setup" fears.