I always feel that we can always learn fast with the videos, demos and presentation than reading a document. We have to read articles multiple times to get a clear understading.

Below are few microsoft links on Ramp up learning series and webcast for Exchange and other related stuff. I hope this will help to get a good understand of the concepts before you hit the documents

http://www.microsoft.com/events/series/tnexchangeserver.aspx?tab=webcasts&id=43235

http://technet.microsoft.com/en-us/ff871920