When learning how to draw is it ok to learn how to draw new things.?

Of course it's okay to learn how to draw new things! I would suggest learning how to draw anything that you'd like to draw, or would like to improve on. Though, I wouldn't suggest using the how-to-draw books unless they're teaching something that can be helpful in any kind of art, like a how-to-draw anatomy or a how-to-use a specific art supply book. Just draw whatever you feel like drawing, and make sure to use a reference if you're having trouble (even professional artists use references all the time.)