Short, sweet, and to the point (well, as far as you could ever expect outta Derrida's writings, anyway), "Structure, Sign, and Play" is a good place to dip your toes into Derrida's ideas. This is where the structure of structuralism all begins to unravel as Derrida points out the silly way philosophers take structure for granted when maybe it isn't there at all. And by dismantling that, he builds the new structure of poststructuralism.
Some questions to keep in mind as you muddle through: is Derrida celebrating Claude Lévi-Strauss, or critiquing him? How does Derrida's style contribute to the points he's trying to make?