I'm sorry, Kovid, but here we do have an issue with special characters again. In this german book, one chapter title begins with a « and this sets the link in the TOC back to 0.
Now, that's no big deal as I just had to change the link target via ncx editing where it belonged, but I really would like to know why it happened in the first place. The book is
here and its the second item in the TOC.