Annotated 9x9 Go Games
There is not much written about 9x9 Go games, but you can find a few videos about them on Youtube.  I would recommend the following series of videos 'Crazy Nines', by Go content creator xhu98:

https://www.youtube.com/playlist?list=PLGTqST4O93ERWgQkCroFSCg4UiOgmL4Mq

The series features Dan level amateur players discussing 9x9 strategy.  This is the best 9x9 analysis I have been able to find.