Questions regarding perspective

I recently decided that I want to learn realism. So I started with Successful Drawing, by Andrew Loomis. He starts the book "teaching" perspective. But thats my point, he doesnt teach. He doesnt explain a thing, just leaves an image and moves on (check page 30). This really demotivated me, so I'm not sure what to do.

First of all, should I really learn perspective right now? Is it something that will help when drawing figures/portaits (I'm mainly interested on the human body only), or is perspective something that only really matters when drawing objects and background?

And what other books or tutorials do you guys recommend if I were to learn perspective? Are all Loomis books explained like that?

Thanks in advance!