Illustrations and explanations:
IMO the best book to start with is Urich & Fisher's Holley Carburators and Manifolds published by HP books. No BS. Urich was VP of Engineering at Holley, and the diagrams and explanations are top notch for a basic understanding of how any fixed venturi carb works. Many finer points are touched on or illustrated as well even though not discussed in detail. I come back to this book and notice things I didn't pick up on before.
You can find a g**gle book version, or go buy the real thing, used or new. Older editions just as good.

There's a great explanation and diagram in a sidebar on throttle relation to transfer slot. If you continue to have issues with off-idle, this is the section to look at. The throttle blade relationship to the slot is very important for idle and off idle AFR. Your Demon may have 'idle-eze' which means that if you can't get the proper throttle-slot relationship, it is not neccessary to drill the throttle plate. Instead you slightly open the idle-eze.