I just reread Suetonius´ Life and a few articles on Caligula.
The other major source is Dio -which i´ll probably read soon. There a few biographies in English too.

Suetonius is full of Black Adder like stuff, the only problem is chronology (when will Black Adder be consul?)Here´s a brief chrono of the reign;

-March 37, Caligula made Emperor
-October 37, Caligula´s illness ends the honeymoon
-May 38, executions of Macro and Gemellus
-38, death of Drusilla
-38-39, Caligula marries Lollia Paullina
-39, Caligula marries Caesonia
-39, Caligula leaves for Gaul. September, Lentulus Gaetulicus and Aemilius Lepidus exucuted for conspiracy, Caligula´s sisters Agrippina and Livilla exiled.
-39-40 Caligula´s German and British "campaign".
-August 40, Caligula returns to Rome
-January 41, Caligula murdered