@Kingston:
Your first question. Something like a Big Mac is bad for everyone. If you study nutrition, you can determine what a good diet is probably to 95% accuracy. The other 5% will differ from person to person due to genes etc.
The variation in the 5% will be due to things like gender, genes, stage of life (child, pregnant woman, etc.), as well as environmental factors like weather etc.
I wouldn't worry about that right now. The majority of "differences" are just excuses. People who don't have the personal will power to tame their pleasure-seeking ego's will use excuses like "Oh I can eat meat no problem" or "There's no way I can give up milk" or "I just can't eat any green vegetables ,they don't taste good" etc. are just kidding themselves. It's like someone saying they can't quit smoking because they'll gain weight. Or they can't quit smoking because their job is stressful.
If you're worried about eating healthy for a long period of time, like a year and still not getting all the benefits because you're consuming a food that you may be allergic to, you can alwasy book an appointment with a Naturopath who works on determining that. Mine determined that I needed to stay away from onions for a while, even though they are perfectly fine for other people.
As for good nutrition books..hmmm.... The nutritionist course I'm taking is offered as a home study course that I can study in my spare time after work. You only need to write the exams on-site. It's not something you have to go to collage for. So if you're really interested in learning everything about nutrition, it is an awesome course. It costs about $2500 if I remember correctly and is made up of 3 parts (Advanced Nutrition, Sports Nutrition, Vegetarian Nutrition). If you're not worried about getting a diploma, the Advanced Nutrition one covers 80% of the material anyways and it's only about $800.
If you aren't interested in learning WHY things work the way they do and just want to learn WHAT to do, the only books I've seen that even come close is Dr. Robert Young's books (pH Miracle, and pH Miracle For Weight Loss etc.), however some of the things that are important he kind of just mentions briefly.
For example, he has a paragraph or two saying "You should supplement your diet with Omega-3 and Omega-6 fatty acids." and that's pretty much it. It's a small paragraph on a couple of pages. If you're one of those people that will do what someone tells them without questioning why, then you'll be ok, because you'll just take the supplements and it will make sense.
To me that didn't work ,and that's why I had to take a nutritionist course in which they gave me a whole fricken encyclopedia to read on Fats (Good Fats, Bad Fats, by Dr. Udo Erasmus). Now when someone says "Saturated Fat" and "Unsaturated Fat", I actually understand the chemical composition of the fats in terms of molecules and it makes sense to me. Before it didn't really mean anything to me.
I don't know, I'm kind of a nut when it comes to studying things in life. When I consider that my family spends between $1200-$3000/month on foods, paying $2500 for a nutrition course didn't seem like a big investment for me. Also, considering the fact that eating healthy will probably extend my lifetime and that of my family by decades, studying nutrition for a few hours on the weekend was a no brainer for me. That's just me though
Tony Robbins also has a good program called "Living Health" which introduces Dr. Young's work and teaches you a complete "Do this and you'll be healthy" course step by step.