This is a lovely book. A page is devoted to each herb and excellent photographs are used to illustrate the parts used.  Clear information is given on the use of the herbs and  Chevallier also provides a practical guide to making herbal remedies.
Published in 2000

The Green Pharmacy 
James A Duke

Duke concentrates on using herbs to treat a wide range of health problems. He gives an honest appraisal of the value of around six herbs per ailment. His style is entertaining and he provides a good deal advice based on his own experience.
Published in 1998

Herbal Medicine – A guide for the health care professional
J Barnes, L. Anderson & J Phillipson  

This book considers herbs mainly from a pharmaceutical view point. It provides detailed information of regarding recent research and clinical studies. Side-effects and contra-indications are professionally outlined for each herb. This is an excellent book for those wishing to go into greater depth.
Published 2002

Out of the Earth
Simon Mills 

Mills conveys in depth  information in a simple, understandable way. He provides a  comprehensive coverage of medical herbalism, including  physiology and the origins of disease,  the traditional view of pathology in which herbal therapeutics have their origins,  chemical composition of medical herbs and good coverage of herbs that may be used for specific illnesses.
Published 1991

Not currently available new from Amazon, but they have links to used copies. Also try the links below.