The terms state the following:
Eligible on Magazine subscriptions only (automatically renewed subscriptions are not eligible). Not eligible on purchases made with coupon or discount codes that are not found on this site. Journals and International Magazines are not eligible.
So you earn 60 bonus AAdvantage miles per dollar spent, plus the miles you’d usually earn for credit card spend, for a total of 61 miles per dollar. That’s a rate of ~1.64 cents per AAdvantage mile, which is pretty great to begin with. If you actually have a use for magazines or can donate them to charity, it gets even better…
This should even be combinable with the promotion offering 2,500 bonus AAdvantage miles when you spend at least $250 through the portal.