A comment on the previous post is one I've been reading a lot from American readers. It is, apparently, difficult to obtain my books over there. The first reason for this is that Tor US doesn't publish them all, it's a shame, but what can I do?
However, some while ago someone directed my attention to The Book Depository which states on its website Free worldwide delivery on every book. If you go on there and stick my name in the search you get most of my books, and they're even discounted. For example, you can buy a copy of Gridlinked, in its nice new cover, for £4.75 including postage and packing. Still suspicious I checked out the 'to these location' bit and the USA is there. In fact there's a huge list of countries there. They also use Paypal.
Now, I haven't used The Book Depository myself so don't know how good it is or how true the promises on the website. I believe others have used it and been satisfied. Please, if any of you reading this do buy books through them, let me know how it went.