The University of Chicago Press offers at least one
free e-book per month that's available to everyone just for giving them your e-mail address. The current freebie is fiction, but the previous 6 or so have been reasonably serious non-fiction titles (mostly cultural commentary and some socio-political history).
I don't know if you'd be able to buy e-books directly from them or they limit actual sales to US-only customers, but it may be worth a try (they've two pricing models: 30-day rental for $7 or keep for full price) and if it doesn't work out, at least you've expanded your possible reading list by one free e-book per month.
Also, welcome to MobileRead!