This was recommended to me, so I thought I should read it. It turned out to be very interesting. The author goes into all sorts of detail about breathing techniques, ancient and modern, all the while threading it together with his own experiment – for a week he breathes just through his mouth and another just through his nose. As might be expected, he feels rubbish after breathing just through the mouth but much better after the nose week. Sorry if I’ve ruined it for you there.
The science seems well researched – although there is always that nagging feeling things have been cherry picked a bit – and there is some interesting stuff about the developed of our jaws etc but the take home message is fairly simplistic. Breathing is good for you and doing it through the nose is a bit better. An enjoyable read, accessible and interesting.