Good news if you live in Germany! Books are delivered free of charge, sometimes even hand-delivered in Berlin, and t-shirt postage is €5, an extra €2 for each additional shirt.
For EU deliveries, it's €9 for a book, an extra €4 if you're getting the two books, and t-shirts are sent registered post for €7.20, with an extra €3 for each additional t-shirt.
For everywhere else, one book is €10.50 to send with registered post, or it's €16 if you're getting the two of them. T-shirts are €7.20 to send with registered post and another €3 for every other t-shirt you get.
I strive to keep postage costs as low as possible. All international deliveries are tracked so you'll get a number to keep tabs on their progress as soon as they've left the Abandoned Berlin HQ.