After a bit of practice I have now completely replicated a DSMapBook application, plus a lot more. So rest easy all you DSMapBook enthusiasts. Some of the functions are still being worked on and renamed after the Pre-release, so there is a bit more to come.
The basic idea is that the "mapbook" is the output document, not the project MXD. So you can load a PDF title page first, then export a series of PDF maps, each with its own MXD with different styles and page layouts, and then the trailing pages. Finally close the output document. Being able to assemble the pages from PDF individual pages avoids having to post process individual maps.
There are additional tools to create strip map and grid indexes, and calculate adjacent sheet names, convergence and other settings needed for a series.
Programming using the high level functions is a much easier than hacking the VB6 code for me because I have avoided using VB. At the same time the available tools are much more powerful that DSMapBook ever was. Especially the dynamic text to allow custom dynamic labels, images apart from being able to switch different layers on for each map. Not the same options form, you have to write a Python script for some things but in the end much more powerful and extendable.