To start this conservation I decided to write a short review of the book of John Seymour, The New Complete Book of Self-Sufficiency: The Classic Guide for Realists and Dreamers, which for me is the absolute bible of self-sufficiency living. Written a few decades ago, it stands as bright and updated as ever, and it features an amazing ammount of information and resources of how to grow your own food, catch water, in very specific, non-sense and practical situations. This is a book for a lifetime.
Another very good book is Perennial Vegetables: From Artichokes to Zuiki Taro, A Gardener's Guide to Over 100 Delicious and Easy to Grow Edibles by Eric Toensmeier. It features an extensive list of many perennial vegetables, easy to grow, how to grow and prepare them, many of which have great potential for permaculture, and are not yet so well known. I have grown some of them this year with excellent results. This is practical Permaculture at its best. I also like very much his detailed style of writting.
Finally, the best general (and a fairly cheap one) Permaculture book for more urban settings, it's 21st Century Smallholder: From Window Boxes to Allotments: How to Go Back to the Land Without Leaving Home by Paul Waddington. This is not only a very practical book but an inspiring one. Particularly for people who live in cities, and would like to get more ecological and self-reliant. The book is divided in the sections garden and food, water, energy, waste, and has many little advices and tricks to reduce our ecological footprint and it also includes a few case-studies. Excellent book to start with.