If one plans to read it only on a PC, I'd recommend getting the PDF version. I think you'll be happier with the format. You can of course easily print out the PDF also, which is a plus for some. I'm reading the PDF on my tablet and computer, and I've also printed it out to more easily see the grand tableau examples at the end.
To buy the PDF version, there is a link on his website to request it. He'll send you an invoice, and then send you a the PDF watermarked with your name and address (to avoid filesharing issues) once you've paid.