Bernal Diaz’ book is a gem, but by no means the only first person account of the conquest. Cortez in his long letters (Relations)) to Charles V, and an anonymous history by “The Unknown Conquistador” are both eyewitness accounts.
The history by The Unknown Conquistador is much shorter, and does not really cover Cortez’ campaign, just a small portion.
At least that was how they were described when I read of them.
Some parts of the story are simply incredible. They're just too unlikely to be true, or, as you namesake put it, "Truth is stranger than Fiction, because it's obliged to stick to possibilities; Truth isn't."