How exactly is the Ismaili daily prayer (du'a) book compiled?

Ismailis pray three times a day at fixed times based on the clock. During their prayers, they read, in congregation (or individually), some sort of book which they call a "du'a book." I don't know much about this book; it seems it has six chapters, the first being Surah Al-Fatiha from the Qur'an, and the last containing the names of all 40-50+ of their imams (ending with the living imam). How exactly was this book compiled, and does it change or remain unchanged throughout the ages?