I found this book to be a very good introduction into the Amazon Web Services (AWS) Cloud Computing platform. I'll admit to be being a little bit overwhelmed by AWS' offerings; i.e., Cloudfront, S3, EC2, SimpleDB, SNS, SQS, etc. This book pretty much clears everything up about AWS in understandable and clear language. It gave me plenty of ideas of how and what I could accomplish in using AWS; i.e., a website, an application platform, private computing resources, and more...
And thanks to Amazon's (recently added) generous 'free tier', my EC2 micro instance is now up and running on AWS! So far, I have not encountered any charges, although this is with light usage on my part. With free utility computing resources at the AWS' free tier, you can actually try out most of the exercises in the book with no (or little) charge.
The CloudFusion exercises as used in the book are slightly 'outdated'; it is now the 'official' AWS SDK and is renamed as such. So, some slight changes may be needed in the code. (Is there an errata online for this book?) This book does assume some intermediate PHP knowledge. There is an overview on cloud computing itself and an overview on Amazon's array of cloud computing services, which I found it to be very useful.
Overall, a 5-star book.