The lore books in The Elder Scrolls series, hands-down.

There is an entire universe of conflicting knowledge, personal bias, and unreliable narrators that leave Tamriel’s history feeling very real, and very open to interpretation. The fun of it is piecing together the truth somewhere in the middle. But I’ll die on the hill that the Arcturian Heresy is absolute horseshit written by a madman, and comparable to the scribbles of a paranoid schizophrenic on an anti-vax forum. Anyone who references that volume in regards to Tiber Septim and the forming of the empire is an impressionable dweeb.