Welcome to MobileRead, and greetings fellow Mac user!
As NatCh said, a lot will depend on the format the site uses for downloading. If it's a .pdf, no problems - that is how I handled my downloads until recently. I also used .rtf from time to time when it was available.
Also, as Nat said, using Parallels/BootCamp (if you have an Intel Mac) will enable you to use Sony's site. And someday, I hope they explain why they won't work with Macs...