Ancestral Health is all about looking backwards and reconnecting to one's heritage as a human being, as Homo Sapiens - not the race Domesticus Fragilus we slowly deteriorate into. While looking backwards we also want to apply modern and qualitative modern findings from science, not some pseudo-ideologies. Therefore, this umbrella term divides itself in many areas that in itself are very complex. One can study circadian rhythms and the effect of light onto one's body for a lifetime.
But fortunately to get an understanding you do not need to become the expert per se. The books listed down below were the ones that helped me form a basic understanding - they provided valuable knowledge, challenging concepts, and great further resources if one wishes to dive even deeper.