This book is EXTREMELY COMPREHENSIVE. If you think that your depression may be due to a nutritional deficiency - and I am very willing to believe that that may be the case for plenty of people in this day of processed food grown in nutrient-stripped fields - this book will almost certainly cover the nutrient that you are curious about. It describes a great number of vitamins and minerals and other items (B12, zinc, low dose lithium, zinc, magnesium, cholesterol, and many, many more), explains their function in the body, describes some of the clinical trials involving the nutrients. and relates the author's experience with specific patients who benefitted from trying that supplement. If you tried to replicate the information in this book by cruising the internet, it would take you a very, very, very long time, and you wouldn't get the sensible overview and clinical experience that the book provides. The writing style is solid; you can tell that it is the culmination of a life's work in this particular field; it does not contain the typos and dumb errors of a book that was just thrown together to make a buck.
Alas, I did not have success trying the supplements described. However, this is not surprising; I come from a very, very long line of very, very depressed people, all of whom ate decent food back when food was not stripped of nutrition by factory farming and processing. Although I am nearly vegan (I already supplemented with B12 and and fish oil and small amounts of cheese in order to avoid ultra low cholesterol levels), I can look at my family and see people who are omnivores who are just as miserable. And, I have success with SSRIs; the problem is that they make me fat and make my blood pressure much, much higher.
I did, however, help an elderly neighbor by giving him zinc, magnesium and B12. He was a wreck - dizzy and trembly. He had been to excellent doctors, including a reputable (albeit useless and unkind) neurologist. Within a couple of weeks of taking these supplements (he stops by daily, so I give them to him) he was much less dizzy and trembly. He lives on breakfast cereal and TV dinners (he is NOT poor!!!!), but I can't change that. I think that the issue for him really is nutritional. None of his doctors were interested in pursuing the nutritional angle, unsurprisingly. They told him to get a cane (!)
One problem with the book, which is really more a problem re the world, is the author's insistence that you work with a doctor and get blood work done in order to properly use the info in the book. Well, that's nice if you still see Dr. Marcus Welby. I have HMO coverage; my physicians are all from developing countries; if a patient hasn't actually slit her wrists she is considered AOK, especially if there is some generic SSRI to prescribe. The HMO does not consider nutritional testing (other than a very few basics) to be something to cover. In my case I could afford to find a private doctor and self-pay, but when you're depressed you aren't really up for that. The reality is that 99.99 percent of people who read this book and do anything with the info, will do it on their own.
The only item that I can add to the book's suggestions is (vegetarian-sourced) creatine. Google "creatine depression" for more info.
The only substance that I think medical science should study for immediate relief of depressed people is prednisone. It helps some people a lot (when used with great care), but there are only a few studies, and it is basically never suggested due to the awful side effects of overuse. However, that would not be the sort of natural item a book like this would cover.
One small complaint: the author considers veganism to be a "fad" diet. He does not consider the possibility that some people are depressed because the world is full of pain and pointless suffering, and that being a vegan is an attempt to improve things. And that it is RATIONAL to be depressed at the sorrow in the world, and it is really quite peculiar that most people can ignore it enough to happily function. However, his focus is on other things, and even an ethical vegan can read this book and likely benefit from it.