Side Jobs is short stories; you can probably get away with reading that at any time. I'd definitely read the others in sequence, though, or you'll get spoilers galore.

The Falco novels are fine read in any order, imo, apart from the latest one which really needs to be left to last - a couple of the later ones are a bit weak but the latest one is a blinder. They're about to start Shadows in Bronze in the 8 o'clock slot on 4Extra tonight if you like radio versions.