Scotland's other drink

In the Ian Rankin novels featuring Inspector Rebus that we've been reading while on holiday, he keeps mentioning Irn-Bru. Finally we looked it up on the Net, because it's obviously a drink, but that's about all we knew. Seemingly it was originally called Iron Brew, and somewhere along the line the name has been squashed. It's Scotland's other national drink (other than whiskey, that is) and is more popular than Coca Cola. It's actually a soft drink, not an alcoholic one, and it's....orange.