In reply to Fraser:
The events in Belle Sauvage occur prior to those described in the His Dark Materials trilogy. However some of the characters are better understood/appreciated by having read the His Dark Materials books first.
I'd also say the tone of Belle Sauvage is quite different. For most readers, I'd suggest reading the His Dark Materials stuff first. However, if the new book aligns well to your Dad's taste, it might be better to read his way in with that. Each of the books stands alone quite capably, though, so no specific order is entirely necessary. I originally read it volume 2, 1, 3 which worried quite nicely in some ways.