I'm reading E. P. Hoyt's U-Baots, a Pictorial History, and one fresh angle for me is the discussion of the personalities of the captains and crew. One particular angle is how the non-Nazi early members were more humble and less elitist (surprise!) than many of the later pro-Nazi members. And Prien was considered a total jerk, with 2/3 of his enlisted men signing a petition to change commands based on his propensity to hand out post-cruise jail time as a regular punishment.
It was also neat for Donitz to use the publicity of Prien's raid to force Hitler into a promise for more subs.
