I found out about this from aromatherapy pioneer Robert Tisserand's facebook page. Right now a few great aromatherapy practitioner or advanced essential oil books are onsale at Elsevier's website. This includes Robert Tisserand and Rodney Young's second edition of Essential Oil Safety, Jane Buckle's Clinical Aromatherapy 3rd edition, and Shirley & Len Price's Aromatherapy For Health Practitioners 4th edition and also their Understanding Hydrolats book! These books are some of the most advanced books we have on aromatherapy, and they are usually very expensive. But right now (not sure for how long) they are onsale for 30% off! The promotional code is AZK3E14166
These are not books I recommend for the absolute beginner but for those with a good solid background in aromatherapy. I highly suggest getting these books if you are serious about learning the art and science of aromatherapy! Robert's book is considered the best, most accurate resource on essential oil safety. Buckle's book was just released and it is already considered a standard and must read in clinical aromatherapy practice. The Prices's books are amazing resources too. Robert and the Prices are considered legends for a reason. Buckle is also an aromatherapy pioneer and a nurse too.