The best starting point I can recommend if you're looking for a general overview of the subject in English is Vladimir Tismaneanu's Stalinism for All Seasons: A Political History of Romanian Communism (Cal, 2003). It's not specifically focused on the Ceausescu era (it's a general history of Romanian communism from the inception of the Communist Party to the Revolution), but it's still a good starting point for learning about Ceausescu.

Dennis Deletant's Ceausescu and the Securitate: Coercion and Dissent in Romania, 1965-1989 is more narrowly focused on the Securitate (obviously) but Deletant's writing is typically excellent and it should still be an informative read.

There's also Edward Behr's Kiss the Hand You Cannot Bite, which I admittedly haven't read.

If you read Romanian, Adrian Cioroianu's Pe umerii lui marx: O introducere în istoria comunismului românesc is also good. It was one of the first books I read on the subject as a graduate student, actually. It's also a more general look at Romanian communism, as the title suggests, but may still be helpful for your purposes.

Hopefully this helps!