You can see an actual nutritionist/doctor and get blood tests. It's probably impossible to determine what is good nutrition from any book besides 'dont eat processed food' because of individual needs/genes.
I've seen a few. It's sort of like hiring programmers when you are not one. I feel like 80% of nutritionists that are 'on the market' are not competent, but I'm not qualified to judge. It's just that they say things that contradict each other, and instead of falling back to some study, they get defensive.