Introduction to Trotskyism?

I've been very unsure about my political stance within Marxism. Though I call myself a Marxist-Leninist-Maoist, I've been reading some of Luxemburg's material on the Bolshevik Revolution and her critique of centralism. And I've been reading works by modern Trotskyist Alan Woods. In short, though I've read Marxist-Leninist material, I cannot find myself able to critique Trotskyism, for example. So I ask: What are some good introductory works to Trotskyism?