This book is well worth reading. I'm taking it slowly, marking up various points of interest, which takes forever, so I'm at p.200, but have dipped into the bits I haven't yet read in detail. Holford's style is matter-of-fact rather than sensationalist, except when he's dealing with the statistics on mental health, which make for sobering reading. Holford worked with legends in the field, such as Dr Carl Pfeiffer and Dr Abram Hoffer (who wrote the foreword), and he's a lot more solid than some people make him out to be.
There are relatively few good up-to-date books on nutrition and mental/emotional health. There's no need for me to over-hype this one. It delivers what it promises, goes into plenty of detail with many pages of references if you want to follow up the scientific side, but if you just want to skim it or concentrate on a chapter dealing with a particular condition such as depression or memory, that's easy enough too. A very useful overview of the subject, and reading it will give you many tools to start to address various issues afflicting mood and mind.