Walter LaFeber's Inevitable Revolutions is an entertaining book that covers the whole region and Bitter Fruit is a decent book on the overthrow of Arbenz if you want some context to the civil war. Might be decent starting points for you. There's also Bishop Gerardi's report Guatemala: Nunca Mas.

To get you started check out the book list. The link is for Latin America during the cold war period but I encourage you to browse some of the other sections of the book list as good books sometimes fit many different categories.

Greg Grandin's book Empires Workshop looks at it in a hemispheric lens

Piero Gleijeses' Shattered Hope is the best you can get on the background to what would become the latter-half of the century's civil war. One of the earliest books I read in my studies and still one of the best, most diligently researched.