I have a very poor memory, but quite good at remembering quirky stuff.
So from the biography of Catherine Medici (The Serpent Queen), I still remember the story about Henry III of France (her son), running away from Polish nobles chasing him because he had also become their King, but did not fancy the country.
Something that helps with recollection etc. is adding to threads and blog posts as and when I come across relevant material on Audible. So, in my Prophet Yusuf post, I added material about the Bengal famine when I came across it in the Dalrymple book. I added material from the Donella Matthews book to the Riba thread.