Since making the post with the Polish cover of Pandemonium, I decided to seek out the cover for Delirium. It’s great!
In my search, I found a link to a US website that specializes is Polish books. So if you want a copy and you live in the US, you can order one of these beauties. Here is the link to Delirium ( http://thepolishbookstore.com/p/130990/delirium ), priced at $17.37 before shipping. They do not have Pandemonium, though. My guess is that it hasn’t been released yet, much like the German (and probably every other translation).