The following is a list of SAFe and Certified Scrum Master (CSM) books MarkNest recommends.
Essential Scrum: A Practical Guide to the Most Popular Agile Process - by Kenneth Rubin
Agile Estimating and Planning - by Mike Cohn
The toughest part of being a scrum master is how to describe the story pointing process to developers for sprint planning estimates. Research story pointing methods and use the best baseline you can to get started.