/sci/ - Science & Math

I don't know very much about chemistry but I did get 94% on AP physics a decade ago. I set out to learn a little bit about the chemical processes that make diesel from crude oil and wound up learning about covalent bonding.
Now, I can roughly follow any Lewis dot explanation of bonding with only a couple difficulties just from having a brain but I've learned that:
>Lewis dot models are a bad approximation
>Molecular orbital theory is a good approximation
When I do a cursory search for molecular orbital theory the only visual models are some kind of energy level diagram like the attached image but the associated text in the places I find them implies that it is typical undergraduate homework to just create such a diagram for some given molecule from first principles with rules of thumb and no DE solving.
If MO theory is that easy, then I can learn the theory from scratch to the point of being able to do it myself before I get bored of this topic.
So
>Have I missed any intermediate approximation theories out?
>If I haven't, can you recommend me a good beginner textbook that has a chapter on the Lewis theory and then jumps to a full explanation of MO theory? I'm not afraid of calculus but I don't know any math beyond it.