Back in the days of the Harry Potter book club, it was indeed pretty much as you say - one thread for every few chapters, then some separate threads for more general discussion of the characters, themes, larger plotlines.
At the time we tried to announce it a few weeks beforehand so as to give people time to get hold of the book, finish other books they're reading, etc. I guess in this case maybe better that you just start and others can join in later. Just let me know when you need me to Announce the thread.