"The Book of the Bivvy" is a half-and-half mix of how to do it and why to do it (or how not to do it, and why not to do it). It presents accounts of bivvybag nights and expeditions, both nice and nasty, alternate with practical chapters about the technicalities of the breathable membrane, how little kit you really can get away with and the secrets of lightweight long distance. The book closes with a selection of bivvybag expeditions to initiate the unwary into the secrets.