Described by the author as "a slightly autobiographical and heavily biased book about investing", Simple But Not Easy has plenty of interest to the experienced professional, and is aimed also at the interested amateur investor.

The theme of the book is that investment is simpler than non-professionals think it is in that the rudiments can be expressed in ordinary English, and picked up by anybody. It is not a science. But investment is also difficult. People on the outside tend to think that anyone on the inside should be able to do better than the market indices. This is not so. Picking the managers who are likely to do better is a challenge.

Richard Oldfield begins with a candid confession of some of his worst mistakes and what they have taught him. He discusses the different types of investment, why fees matter, and the importance of measuring performance properly. He also outlines what to look for, and what not to look for in an investment manager, when to fire a manager, and how to be a successful client.