Here are a two starting points:
- Exchange 2010 – A Practical Approach. Thank you XLA for locating this.
- Microsoft Exchange Server 2010 Administrator’s Pocket Consultant. Easily the “bat book” equivalent for Exchange.
A Unix guy dives into MS Exchange 2010
Published
Managing organized complexity 
The exchange guys also post useful info here:
http://msexchangeteam.com/default.aspx
The Windows Server System Reference Architecture is also a very useful guide.
How come?
It’s a messaging architecture, therefore I have to “speak” it.