Dengler is a really compelling speaker. His experiences are presented fairly plainly, with some moments of line blurring weirdness as he recreates some of his capture. There's a sadness in the moments where he discusses things such as only being able to sleep in a plane cockpit and all the food he keeps in his house, the lasting effects of his trauma.
Herzog's narration is minimal, leaving space for Dieter to be himself and tell matter of factly of his suffering.