I count my blessings when I find all the books of a series in one go in the second hand bookshop. Even more so because I had already looked for more Charles Stross books and decided there weren't any in the shop. It was only another bookish customer remarking to the shopkeeper how unusual it is to see Charles Stross on the shelves that I realised I'd been looking in the wrong place!
The first book of the pair is Singularity Sky. We join an engineer and an Agent of the UN as they meet and try to save a planet in their own way. The planet is under attack, but quite how it is under attack is the weird Sci Fi bit. Very clever story although for some reason I found it quite hard to get into at first.
Scroll on one week to the second book, Iron Sunrise. This has our same two heroes and introduces a third unlikely teenage heroine. An tragedy (unrelated to the first book) has befallen her home world and another tragedy will follow it unless all the good guys figure out how to beat the bad guys. Bad guys aren't so bad, just misguided in a brainwashed sort of way. Very Sci Fi technology but remaining believable, these books are worth a read though if pushed I'd put Glasshouse a peg above in your wish list.