where can i find 72 pages book

Hi, Santosh! Welcome to the course. The official whitepaper is "Overview of Amazon Web Services." You can find links to it within the "Understanding Cloud Computing" lesson in two places: as a resource link and as a blue clickable button titled, "Read Whitepaper." You can also access it here: https://docs.aws.amazon.com/whitepapers/latest/aws-overview/aws-overview.pdf. I recommend that you read it in full before the exam and then do a quick review the day before your exam. Best of luck to you!