Michael McFadden at 2012-11-09 11:28:38:
Linda Aronson has written an insightful book on the subject of multi-linear, non-linear and multiple protagonist story structures which she terms 'parallel narrative'.
http://www.amazon.co.uk/dp/1935247034
There is also plenty of great information on her website here:
http://www.lindaaronson.info/main/page_the_six_sorts_of_parallel_narrative_.html