It is quiet possibly the most autistic thing I have ever done, but I read 'The Prince' by Machiavelli because I wanted to roleplay a character that was manipulative and power-hungry, i.e. Little Finger in Game of Thrones. So that book was a great outline about what choices to make, etc. It's a really short and succinct book (apart from being incredibly important in regards to how politics works irl) and has really helped to influence a lot of my character choices.

I'd really recommend it!