Welcome to the boards.
I'd recommend putting aside The Ethical Slut and grabbing a copy of Opening Up, by Tristan Taormino, instead. TES gets way too frou-frou, in my opinion, and Opening Up is a much better read.
Let your husband read it. I suspect that will go a long way to addressing his fears.
As for getting through it, that requires persistence and communication, skills necessary in any relationship and doubly so when juggling multiple relationships.