Break down what you want to learn, for what I've seen, no single book covers the massive genre of people photography comprehensively enough to be considered a sole resource.
Even from your post, portraiture and fashion photography can be similar, or miles apart, depending on what you want to shoot and where your inspirations come from.
Find somebody you like, portraits could be anyone from Rankin, to Uli Weber, to David Bailey, literally anyone, but someone who's style you like. Then study their images closely, regularly, and evaluate what you like about each image, and identify how their style comes through in each shot. When you do this, research how they shot, where they shot, who they shot....
A fundamental understanding of exposure, dof and lighting is required of course, there are lots of books on these individual subjects and I personally would advise that that's how you approach it.
Light, science and magic. Buy it, read it, re-read it. Learn to love it. Once you understand the characteristics of light and the ways you can effect it, you can work everything else out for yourself.
If you struggle with poses, find shots you like, pose wise, and use them as a reference. Everyone does.
In the fashion industry you will hear reference to moodboards and storyboards, basically they're a collection of reference material,usually visual. Don't copy, don't imitate, but do take inspiration and lots of it.
Start taking pictures, send them to people who are qualified to appraise them. You will find people happy to critique and appraise your progress. Don't chose friends or family, and dont chose a landscape photographer because they're traditional, have no creative energy, and only shoot by the rules (JOKING!!!!!) lol.
Total waffle, and probably utter rubbish. Take it or leave it lol.
Regards
Danny
