[sandreas]

Well, if you own the epub, you could try to find out the whole length of the audiobook, then extract the whole text of the epub splitted by chapters and then relatively match the text length to the audio length and put the chapters where the nearest silence is (chapter 2 is at 3.3845% of the whole text, so seek for a silence around 3.3845% of the audio length)

I got some pretty good matches with m4b-tool here, while it does not work for all audio books (you need the latest pre-release for this very experimental undocumented feature!):

  # try to match my-book.epub on my-audiobook.m4b
  # ignore first, second and last two epub-chapters for the match (dedication etc.)
  # split chapters into sub chapters to ensure they are between 5 and 15 minutes
  # create a backup of the original chapters (done automatically)
  m4b-tool chapters -v --epub=my-book.epub --epub-ignore-chapters=0,1,-1,-2 --max-chapter-length=300,900 "my-audiobook.m4b"

  # omg it did not work and messed up all chapters, please restore the original chapters
  m4b-tool chapters -v --epub-restore "my-audiobook.m4b"

  # ok, lets only dump the findings in chapter.txt format to do it manually
  m4b-tool chapters -v --epub-dump --epub=my-book.epub my-audiobook.m4b