If you're interested in learning about Garak and Andy's later career, this probably isn't the book for you. It covers his childhood, education, and his life and career up to the mid-80s. It also refers to his current teaching and how the earlier subjects inform it.
I think it ends in a good place, thematically -- he talks about playing a difficult killer in The Belly of the Beast, and how different it was in the performance and the aftermath than playing the Scorpio killer.
Reading this book, and having read A Stitch In Time, I was fascinated by how much of himself he'd put into Garak, as characterized in ASIT. There were a lot of parallels, and I can really see the acting process he's describing in the book working in ASIT.
Basically, if you're interested in Andy as a person, and/or in his artistic process, Stepping Into The Light is a book I personally found satisfying and would recommend.