Probably depends on the book. Some publishers have their own offerings that, as far as I can tell, do not require one to have any other software.
Paper v. Electronic (PDFs and PGNs)

Probably depends on the book. Some publishers have their own offerings that, as far as I can tell, do not require one to have any other software.
Which publishers? I'm looking at some books from Everyman Chess.
I once obtained some sort of an electronic Everyman book, and I was able to use it without buying any other software. That was a long time ago, so you should probably go to the Everyman site to see the current situation.

Just checked. The Everyman site does indeed have PGN, CBV, and Kindle formats for sale for a lot of books. That's nice. Not sure about the other publishers, but the big ones probably do as well.
CB does not run natively on the Mac, true. You need a virtual machine (e.g., Parallels) running in order to run PC software such as CB on your Mac.
There are several opening books (repertoire or otherwise) I may want to purchase eventually (some of them are by Everyman Chess or other major chess publishing companies). Ideally, I would have a paper copy (hard copy), a PDF version, and PGNs. I don't have ChessBase at this time, but the next time I upgrade my Mac I may look into if if that's helpful. What are my options with or without ChessBase? Are these things (hard copy, PDF, PGNs) I have to purchase separately, and are the PDFs and PGNs hard to find or do they come with the paper books (not seeing them on Amazon).