Hm, that's strange – the resulting HTMLs from huffdic compressed e-books from HarperCollins are twice as big as they should be. I looked at the generated HTMLs and found out that after they should end, the books start again with the table of contents like:
Table of Contents
Table of Contents (this and the following content shouldn't be there)
You can test this with the free e-book Flight of the Nighthawks
by Raymond E. Feist.