I've just finished with the books Liar's Poker by Michael Lewis and Conpiracy of Fools by Kurt Eichenwald and I would reccomend them to any investor. Liars Poker is more of a fun read, but give invaluble information on how many Wall Street firms are run. Reading Conspiracy of Fools is one of the greatest ways an investor can spot possible duds such as Enron. If you read this book, you may not know exactly what is going on in a company, but you may be able to tell if something is just not right.
Watch for my full reviews on both books being published soon on SA.