I second this. I finally got around to putting together some ePubs last week, and after a few hours of hunting the web for advice, I finally just bought her book.
The book has a whole part covering InDesign CS 4 and 5, and throughout the rest the author consistently points out areas where InDesign's output must be hand-tweaked in order to work properly.
I am actually building my books by hand; I don't use InDesign or Sigil. But I still find the book incredibly useful as a reference. Well worth the $20.