I actually think that the combination of a book, and a teacher (but this is the sort of subject where - if you connect well with the teacher, and feel safe when making a mess of things - it can make an enormous difference to you enjoyment of and appreciation for the subject) works best.
Art - drawing, sketching - is one of those subjects when you benefit most from having someone at your shoulder to point out how you may need to do things differently, how much of a difference one line in the right place can make, and watching closely how they may choose to correct lines on your page that aren't working - all of this is enormously instructive.
Try a book first. There are countless books on learning to draw, and have been for many years.
Two that come immediately to mind:
Drawing for Dummies
Drawing on the Right Side of the Brain
Both are available on Amazon. Many public libraries have them, or books like them, too.
I'm not so much disagreeing, but I'd emphasize something else before any of that.
JUST DRAW!
Keep doing it when you can.
It's when you think you see what your shortcomings in your work, you start 'creating' your style. You may like a more angular look, softer, perhaps you prefer shapes, it's an endless list of options that may dictate for you how you draw.
The problem with books often is that they in a way teach you someone else's style.
Teachers will always recommend life drawing, because it's just your perception of things, put on paper. A model though is NEVER wrong, it's real life, and you try to get as close to that as you want to. Even then though, you will still be applying your own preferences, which is your style of drawing.
Ultimately though all the resources in the world don't mean a thing, if you aren't drawing constantly. It's then the willingness to correct anatomical shortcomings, bad habits in style, that you start to get better.
Just draw.
You literally can NOT, no matter what anyone tells you, do it wrong.
You are only drawing wrong, if you aren't at all.
When you start drawing, if you want to keep doing, that will motivate you to then look at books, maybe ( trust me, people do have a stigma about drawing models, especially nude ones ) live models, and then discover what type of you prefer... digital, pencil, watercolor, whatever.