The I Ching, the ancient Chinese oracle, or Book of changes postulates that everything is in constant flux, moving from state to another. Whilst being proven as a working oracle for more than 3000 years, it is not the work of a single author but the accumulated wisdom of many generations. 'The ancient chinese sages realised that change itself gives meaning to life and contains an element of stability, an inherent law or eternal principle, which people tried to find outside the world in a realm of transcendental reality' John Blofeld in the Foreword to his book.
I have used the I Ching for more than 30 years and found it an invaluable and infallible guide to life. In particular it has proved useful facing difficult life dilemmas. If treated seriously and with due reverence, it will unfailingly guide you to find clarity from your own confusion. It is however a book demanding serious reflection and meditation and not for foolish questions or play.
There are many interpretations available. The Classic one is that by Richard Wilhelm with a foreword by Jung and has an ancient and symbolic feel to the text which takes getting used to. This is ISBN 07100 1581 X
The John Blofeld translation is cheaper and simpler, but I have always found it useful. ISBN 0 040181026 0
The more recent Element book by Rudolf Ritsema and Stephen Karcher is very good for symbols, but can be complex. ISBN 1 85230 526 3
However the most useful and understandable modern translation is by Carol K. Anthony called A Guide to the I Ching. This is in paperback ISBN 0 9603832 4 7