The Book of Changes, or I Ching, is one of the oldest of the Chinese classic texts.
In China the Book of Changes had two distinct functions. One was a divination text used by the marketplace fortune teller and roadside oracle. The other was as a compendium and classic of ancient cosmic principles used by the educated Confucian elite.
It can serve these two function because the 64 hexagrams of the I Ching are an ordered set of universal archetypical situations. If your personal situation can be related to one of the archetypes, either by reading and interpreting the hexagrams, or by randomly selecting them, one can apply the wisdom of the appropriate hexagram to your own situation.
I personally favor something of a combination... randomly generate hexagrams, then let your mind and imagination explore those hexagrams to see if you can see any correlation... If nothing strikes a chord try again.
The variety of situations is vastly increased by the fact that most divination methods produce two hexagrams, related by which lines of the hexagram are "changing".
This online mobile I Ching used the 1882 pubic domain transation by Dr. James Legge of Oxford University.