Hi, Ian!
It'd be the best written northern soul related book ever, that's for sure!
I think that a book like this would have a lot of "crossover" potential and would help to "spread the faith" more that anything else i can think of...I do work as a musical journalist in Spain, i read loads of music related books and articles every month... and, believe me, writting like yours is one in a million, congratulations!!
Best!
Edu