As with most Stross, they're pretty dense, and this even more so because in the first you're beginning a new science fiction universe, so you don't initially know when or where you are, what's happened or what's capable of happening. Once I learned the environment, I found it fairly interesting – at least enough so to read the second book. As the second is built largely around the protagonists of the first, it's much easier to follow and actually more enjoyable. The main problem I run into is that the depth of Stross' writing – the technology, the things that have changed, and so forth, get me thinking what parts of the book I would edit outt to make it easier to follow. There are characters and subplots that just clutter the books up, and make it much harder to follow.
Still, they were okay. Just started another Stross to kill time until we get the next Laundry novel.