Rating: 
Summary: A good first book on the PDE approach to derivative pricing.
Review: Wilmott's Derivatives is an accessible introduction to the partial differential equation (PDE) approach to mathematical finance. The basis of mathematical finance is the observation by Black and Scholes that when pricing a derivative contract, for example a stock option, the randomness of the value of the underlying stock can be used to balance the randomness in value of the option in such a manner as to eliminate all randomness. A trader can thus by continually rebalancing his positions guarantee the price of an option. This price is the solution to the famous Black-Scholes equation. Thus the pricing of derivatives becomes a suprisingly rigourous branch of mathematics. The Black-Scholes equation itself is not a particularly difficult equation -- indeed a few simple changes of variables transform it into the one-dimensional heat equation and a closed-form solution for the price of an option can be written down. The proof that it holds and the implications of the proof are however not so trivial and the book does well at explaining these. Mathematical finance does not end with the Black-Scholes equation for two reasons. The first is that more and more complicated derivatives products are continually being innovated which require new mathematics to be invented. The second is that the equation is based on certain assumptions which while providing a reasonable first approximation are not perfect; the research of new more accurate models is therefore active and ongoing. The author starts with the definitions of the basic financial instruments and gradually builds up to the Black-Scholes equation. He does so in a clear and detailed manner. He then goes on to discuss various generalizations to exotic options and more complicated models of stock price movements. The principal defect of the book is that mathematical finance is not a branch of PDE theory or applied mathematics but rather a branch of probability theory. The probabilistic aspects of the subject are skimped on with only a brief coverage of binomial trees, and the concept of an equivalent martingale measure which is the fundamental concept of mathematical finance not discussed. Interest-rate options and many exotic stock options are more easily priced both practically and conceptually from a probabilitistic point of view and the PDE approach to them can become contrived. To summarize, this book is worth buying but the reader should treat its contents with a pinch of salt and concentrate on the first two hundred pages. It should be read in parallel with another book, such as Baxter and Rennie, which concentrates on the probabilistic approach to the subject.
| 
