Okay, hot take: the Protheans are overrated. Their history is just a repeat of the Reaper cycle. Empire rises, gets complacent, gets harvested. The interesting history is happening now, with the current cycle fighting back. The novels focus on that present struggle, which is why they're more about Saren, Cerberus, and the Illusive Man.
We don't need a Prothean history novel because their story is functionally identical to every other cycle's story. The tragedy is in the repetition, not the specific details of their empire. The novels hint at that cyclical horror, which is more powerful than any one empire's biography.