Microsoft released a free e-book on Windows Azure for IT Professionals. The 130 pages PDF file has 6 chapters and can be downloaded here.
The book covers all areas of Azure. Each chapter has an high level overview of the services. By reading this book a good overview of Azure can be obtained, It is a technical book without marketing language.
The chapters are:
1. Understanding Windows Azure
2.Windows Azure compute services
3. Windows Azure network services
4. Windows Azure data services
5. Windows Azure app services
6. Getting started with Windows Azure