While the Scrum Guide gives the rules, I think that the stories in Ken's "Agile Project Management with Scrum" is still very helpful to learn the mindset. It will help you understand it rather than just learning about the rules.
When I think about my own journey to understand Scrum better, I have read a lot, and while this has been useful, many key insights have been when talking to others. Thinking about problems and real life situations, sharing experiences and ways of thinking.
If you have someone to work with/discuss with, check out these study questions I prepared for people that wants a structured way to work through many aspects of Scrum: http://www.cedur.se/scrum-skills-series.html