Well, I read this book more then 10 years ago and loved it so much that get the whole book photo copied (at that ebook was fantasy, for me at least). I still have that copy but content of this book are still fresh in my mind. Regard it as the most detailed work on how/who/why Islam was divided in Sunni/Shia. Madelung used almost all authentic sources for his research which is so much important to make your point.

Anyone who wants know why/what happned right after Prophet Muhammad (PBUH) passed away, do read it.