Principles of Financial Engineering by Salih Neftci
Neftci presents a good walkthrough of using financial products to achieve a goal; here, the goal is typically trading-oriented as opposed to hedging-related. A good intermediate textbook, Neftci uses news articles to test your understanding of the material, so the financial blurbs in the FT will start to make some sense.
And no, I'm not going to quote a bunch of equations. ;)