http://www.amazon.com/gp/product/0393352242
Edit: WSJ Review: “Talk to 10 money experts and you’re likely to hear 10 recommendations for Burton Malkiel’s classic investing book.”
If I had to recommend _one_, it would be Four Pillars. The first part is a bit more intellectually "challenging" than Random Walk, but ultimately does a better job (IMO) at backing up the author's ideas on personal investing with data.
Random Walk covers all the major bubbles in history, and does an excellent job at breaking down asset allocation per age range in the later sections of the book.
All About Asset Allocation was very useful to me in developing a long term investment plan, and deciding what asset classes to include in my portfolio.
I refer to each book at least once a year.
Malkiel believes in investing over gambling/speculating. That means trying to obtain market returns rather than trying to beat it, using very-low-cost funds like those offered by Vanguard. A great place to read more about this philosophy, when you finish Random Walk, is the Boglehead's forum.
And it really does depend on how deep down the rabbit hole you want to go. I do equity research now... feel free to contact me.