Midway between a road bike and a full-on tourer? I've just bought a Thorn Audax and I'm very happy with it. It's heavier and comfier than my road bike, with mtb-style low gears - and because I know I'll never go touring carrying everything but the kitchen sink I didn't want/need a full tourer. I wanted it for a bit of touring, where I travel light, and I do FNRs and occasional audaxes on either one, audax bike or road bike.
As I understand it the main differences are that the Audax is lighter than a full touring bike, though still a steel frame, a bit more sprightly but not as much as a road bike, will carry light-to-medium weights of luggage, and usually runs on narrower tyres than a touring bike. I'm sure someone more knowledgeable than me will be along soon to take issue with some of that though.