My default book of reference is the Bible. At the risk of proselythising, if you search the internet for any situation or phenomena ever happened on the surface of the earth, there are verses and precedents. As things unfold in the present world, I am continually amazed at how accurate the biblical expositions are.
I have read the Christian Bible cover to cover many times, in a variety of translations. I've also read parts of it in another language. For good or ill, no other body of literature has impacted western civilization like the Bible. The church was, after all, the driving force of culture for a very long time.
I prefer something more useful, like the SAS survival guide and the Complete guide to self Sufficiency by the late and great John Seymour.
I actually carry three books. The SAS survival guide, A book called a Pocket Reference by Thomas J Glover and a Bible. Heart,mind and soul. All three are in small size and easily carried.
The Jefferson Bible is a lot smaller, easier to carry and contains the wisdom without the BS. Jefferson was a wise man.
I'm a traditionalist and like the King James Version. I have one that is no bigger than a deck of cards. I'm afraid though that I find much in Jefferson's beliefs that I agree with. Like him I am more Unitarian than Christian. I guess I am sort of a Jesuit Unitarian or Jesuit Pagan.