There are many blogs, videos, Quora posts discussing the similarities and differences in both the practices. SRE was developed by Google for internal consumption and overlaps with the DevOps culture and philosophy.
True to its title - this really is a non-programmers guide. You could even say, a non-technical person's guide. It's a bit about Agile practices and DevOps - but if you're already doing anything remotely related you likely won't get much new out of this book.
If it's new to you and you're non-technical, it may be worth a read.