What books had the biggest impact on you (other than scriptures such as the Bible and Koran)?
Although several fiction and non-fiction books have had an impact on me, the biggest influence in the last 10 years (or so) is probably Man and His Symbols by Carl Jung.
http://en.wikipedia.org/wiki/Man_and_His_Symbols
The thing that I particularly like about the book is that it was not written for the professional psychologist but for the layperson, which I am.
For those who want to read more about who Jung was, his autobiography -- Memories, Dreams, Reflections – is recommended.
http://en.wikipedia.org/wiki/Memories,_Dreams,_Reflections
And, there are numerous online sites with info on Jung and his ideas.