At the moment, both trades are only available for digital download, and the print versions are only available to people who pre-ordered them online. They should, however, be available for purchase tomorrow at comic shops, along with tomorrow's new comics.
Here's an exclusive preview of America vs the Justice Society in case you are still on the fence on whether or not to get this. In my honest opinion? The fact that it's a well-crafted story that examines the history of the Justice Society on Earth-2 and allows Helena Wayne to function as a lawyer are two of the major selling points of this miniseries!
Also, I'll start reviewing this mini this week! :)