/ic/ - Artwork/Critique

I am a complete failure at art, been trying on and off for a while now (haven't reached a 100 drawings yet) and I was wondering if copying that Micheal Hampton book would help me improve my art and actually allow me to create nice looking images of models and characters that I like (mainly models to be honest).
Is it worth the time investment? I am a pretty slow person, so 3-4 copies will probably take me two days/sessions and I'm planing on copying the whole book. I also don't quite understand the theory so I was hoping that actually drawing it would help me fill that knowledge gap.
Here are my copies thus far, so feel free to judge and whatnot (not sure what you can say about a copy to be honest, but go ahead).