Tough Question because there are soooo many!

There is overlap ofcourse between many books.  However, I particularly like "Four Pillars of Investing" by Willliam Bernstein, for the time he spent on the History of the Market.  It is very interesting and important for any investor to understand.  The continous bubble cycle was just amazing.

My latest book I found to be a great resource.  "The Five Rules for Successful Stock Investing" by Pat Dorsey.  If one is interested in individual stocks, this book seems like a good one.  It had information I had not seen in any of the other investing books I have read.  Ofcourse, I have not read allot on investing in individual stocks either.

Good Luck all.

Brian