meaning of '...suggested I'd have to write down toward some Common Denominator.'

[Sympathy]

[Sympathy]

Below is the next paragraph:

[Anchorman]

Hi, I think that "write down" here means to re-write the book in a simpler form. The "common denominator" is related to this and means the level at which most readers will understand. The last sentence means that this level will be very low and implies the readers have the intelligence level of apes (writing by holding crayons in their fist, and dragging their arms on the ground). The term "dash it off" means to write something very quickly without giving much thought to it. Hope this helps.

[Sympathy]

Awesome. Thank you very much anchor.