Sunnis and Shi'a

Not sure if this is the right fit?

Consider Accidental Presidents by Jared Cohen. Recommended by 10 sources.

“Accidental Presidents offers eight narrative portraits of men who succeeded to the U.S. presidency without election, using anecdote-rich scenes and readable context to show how personality and circumstance interact with office power. It’s strongest as a set of self-contained stories that make succession stakes concrete for non-specialist readers; it does not prioritize dense archival argument or exhaustive methodology, so expect some interpretive generalizations and repeated themes across cases. Use it for fast historical orientation rather than scholarly deep-dives.”