After watching Anthony Bourdain's "Parts Unknown" episode on the country I'm very interested in learning more about what life was like under colonial rule.
For a historical resource check out UNESCO's series: http://www.unesco.org/new/en/culture/themes/dialogue/general-history-of-africa/volumes/#c181073
Also, check out:
The Fate of Africa
As someone who grew up being able to see the erupting volcanos in Zaire, I'd recommend some of the following:
King Leopold's Ghost
Through the Dark Continent
The Congo: From Leopold to Kabila
I can also recommend some more recent books, including:
Dancing in the Glory of Monsters
Blood River
The Poisonwood Bible
etc.