4 "books" in the game. Sothe and Micaiah for the first, someone else for the second, someone different again for the 3rd, and then all three lines weave together for the 4th
But yeah. The number of characters that you can allow to die without losing something from the story is relatively small, so i'd just hit that Home button and choose "Reset" whenever anyone bites the big one, unless they are an Ally or an Other unit. You can let them destroy themselves until the cows come home, unless keeping them alive is part of the success requirements

Monster Hunter: pissing me off since 2010.







