For those looking to dive into the books, you can find a list of Sara Shepard's Pretty Little Liars books on Wikipedia.
The first half concludes the original mystery, while the second half jumps five years into the future. Index Of Pretty Little Liars
The massive success of the original series spawned an entire television universe. If you finish the main index, you can dive into these companion series: For those looking to dive into the books,
Focus: The disappearance of Alison DiLaurentis. Index Of Pretty Little Liars
Alison returns to Rosewood and tries to adjust to normal high school life, but her web of lies quickly catches up to her. Tensions rise between Alison and the other Liars, culminating in a murder trial that threatens to put them all behind bars.