Output formats of chm2pdf

Question

On Ubuntu 10.10, I am trying to use chm2pdf 0.9.1 to convert a chm file into a pdf file.

The hint of the command says that

Either '--book' or '--webpage' or '--continuous' MUST be given!

Its help document further explains:

   --book Specifies that the HTML sources are structured (headings,
          chapters, etc.).
   --continuous
          Specifies  that  the  HTML  sources are unstructured (plain web
          pages).  No page breaks are inserted between each file or URL in
          the output.
    --webpage
          Specifies  that  the  HTML  sources  are  unstructured  (plain
          web pages). A page break is inserted between each file or URL in
          the output.

1. I first tried '--book' option, but

   $ chm2pdf --book 1.chm
   ERR002: Error: no pages generated! (did you remember to use webpage mode?
   Something wrong happened when launching htmldoc.
   exit value:  256
   Check if output exists or if it is good.
   Done.
   

   I also tried this option on other chm files, and all failed. I wonder why and how I can get the nice book format output? My htmldoc version is 1.8.27.

2. I then tried the other two options --webpage or --continuous. The output of both are both broken down into pages, except that with --continuous there are fewer pages, and the files look no other differences to me. So I wonder what do they differ actually?

Thanks and regards!