Travellers' Health: How to Stay Healthy Abroad (Revised)

This book gives you a plain English overview of all the major illnesses which may affect the traveller and is very easy to understand. I found the appendices particularly useful as these provide you with information such as drinking water safety and the relative risk of disease country by country. Interestingly, the book also gives advice on accident avoidance and other less obvious hazards (e.g. UV light and acute mountain sickness). If you want a book that you can rely on to give you the facts while 'in the field', I would highly recommend this one.