Some changes have to be made to chopbook to allow it to import older books. 1. It needs to be able to set the link target of a chapter. This depends on https://bugzilla.redhat.com/show_bug.cgi?id=885564 2. It needs to import custom entities 3. It needs to detect duplicate images. This depends on https://bugzilla.redhat.com/show_bug.cgi?id=1035547
A lot of the work required to import books without creating duplicate topics has been done at https://github.com/pressgang-ccms/chopbook. I imagine this code will have to be rewritten at some point, but it is a good place to test the logic required.
Chopbook has been replaced with a Javascript based application which is checked in to https://github.com/mcasperson/PressGangCCMSImport. The original chopbook will be discontinued.