Sorry for late reply, yesterday we had day off.
To make import with custom fields you have to add these custom fields to Book Library component, change structure of XML file and finally import your file into Book Library.
This could be done as custom work.
If you want to get a quote, please send to our contact form needed fields and their detailed descriptions (what exactly they must do) and we will estimate the price of this custom work.
If you have other questions, don't hesitate to ask me.