Red Gate softwares have released a free eBook called "Exchange 2010 - A Practical Approach" by Exchange MVP Jaap Wesselius. It provides all you need to know about Exchange Server 2010 and email archiving, topics include: getting started, what has been removed, new features added, Exchange Server 2010 and Active Directory, Exchange Server coexistence, Server roles. I’ve embedded this eBook below:

"Exchange 2010 - A Practical Approach" and Exchange Server Archiver trial -