I have not put this down since I received it. Yes it is a bit over my head as I am no chemistry major, and I find myself having to look up many words to know what they are talking about as it written like a textbook. But, it is all based on facts and studies, gives recommendations on whether it is actually safe or not orally, skin sensitivities, the safe amounts, etc. As I'm new to essential oils, I wanted to do it right, without all of the misleading info I was sure I was seeing on some EO pages for big oil companies. After reading a few pages, I know those companies are pushing products unsafely at times, and I am glad I purchased this book. You can't put price on this kind of quality. I bought a used version to save a few $, but still worth every penny!!!!!.I just got myself some tabs for easy finding of pages, as I have to go to glossary a lot, and it is a huge book. It has already made it easier, and not so overwhelming. I am already finding other books I've purchased recently inadequate comparably.