BACKPACKING AND LONG-DISTANCE WALKING
Based Chris Townsend's decades of experience as a walker and equipment reviewer, this is the most comprehensive guide to walking trails. Although the author is British it's written for the US market, but anyone who spends time in the outdoors will find much to learn here.
MOUNTAINEERING, BACK-COUNTRY SKIING AND KAYAKING
A 620 page monster, this tour-de-force has been the go-to resource for over half a century. Drawing on the collective expertise of The Mountaineers club of Seattle, it covers just about every outdoor topic with all the detail you could wish.
My ancient edition contains one of my all-time favorite quotes:
A true mountaineer is never lost (though they may be temporarily disoriented for a few days at a time...)
If you lead groups into wild country, you owe it to your party to study this book with care. As the handbook for the UK's mountain leadership certification, it has evolved over a number of editions into the Bible of it's field.
Widely regarded as the definitive resource on the topic. Brotherton is a highly respected expert who trains SAR teams and Special Forces around the world. The book is based on this experience.
It covers every aspect of land navigation with authority and lucidity, and also recommends safe and effective ways to develop and practice the techniques.
It's lavishly produced and a pleasure to use - but avoid the Kindle edition as the layout is a mess.
I thought I was an expert navigator before I read this book - now I realise I'm a mere beginner. If you venture into wild country navigation can be a life-or-death skill, and The Ultimate Navigation Manual is the fast track to high-level expertise.
FITNESS AND ENDURANCE
If you stretch yourself in the hills, this is the book for you. A comprehensive guide to training for mountain adventures, and by far the best in its field.
I'll take this opportunity to alert people to a classic that's little known outside of Scotland:
Written by Everest pioneer Bill Murray on toilet paper in a German POW camp during WWII, this is an extended meditation on why we are drawn to the beauty of the hills. Poetic, witty and gripping by turn, it entranced me as a schoolboy and belongs in the very top rank of mountain writing.
Still in print, and available on amazon.co.uk as an inexpensive Kindle edition.