The Court Jeweller's list of royals writing autobiographies is:
Duke and Duchess of Windsor: Nazi sympathisers and generally unlikeable. Edward walked out on the Crown, wasn't entirely forthcoming with details of his finances, argued pretty regularly with George VI about money and spent the rest of his life drifting aimlessly. Not a good precedent to follow.
Princess Marie Louise: Pretty discreet. Divorced her husband but to this day no one is exactly sure why, despite publishing her memoirs.
Princess Alice: Also pretty discreet and uncontroversial.
Diana: Not sure the Morton book worked out well in the long run for her, although I appreciate that's a matter of opinion and other posters may disagree. Not in my opinion a good precedent.
Fergie: Pretty unpopular before and after the book being published. Also needed to make money pretty urgently post divorce from Andrew. Also not a good precedent.
They don't add in Charles as he obviously didn't write the Dimbleby book himself, but this didn't do anything to improve his public image.
So we've basically got a mixture of minor royals publishing discreet memoirs as they come towards the end of their lives, or controversial royals trying to improve their public image. Time will tell of course, but emotions are obviously still raw on both sides and I suspect this won't do anything to improve Harry's image more generally, or his relations with the rest of the RF. Of course Harry may have decided that he is ok with being permanently estranged with his extended family.