Gosh, well there are plenty of books I have thoroughly enjoyed and gone back to read again, but a LIFE-CHANGING book! Lets have a go.
Thomas Paine's Common Sense and The Rights Of Man - I read this on the day of the Queen Mother's funeral which is a fine irony. Its a treatise from the C18 about the lack of justification in the Monarchy. The book and Paine himself influenced the formation of the USA and the French republic.
John Stuart Mill's essay on Liberty - a somewhat rambling piece, but the take home lesson is that absolutely everything (Islam, Christianity, Democracy, whatever) has to be questioned and challenged or it has no validity. It becomes dead knowledge.
Elizabeth Gaskell's Mary Barton - a scathing polemic against Victorian politics and social attitudes that makes Dickens look like a simpering liberal. The odd thing is that Gaskell's other books are rather Jane Austen-like.
Nothing really bushcrafty I'm afraid, but I have enjoyed some rather good travelography. The best of which was Passage to Juneau by Jonathan Raban.