Well its not out yet once its out on DVD & Blu Ray you can then download it off the PSN network, Zune store, itunes, amazon etc.... Or just buy it the first week it comes out in stores usually cheaper the first week of sale by a significant margin with most retailers.
Since its only been on showtime torrents are the only way you can get it unless you have showtime you can probably on demand it or find someone who's dvdr
Comes out Aug 17th if you can wait
Fantastic show probably my favorite show and season yet. John Lithgow was perfect and so was Michael C Hall.