This prestigious award covered all series ending between 2015-2017.
From the Aurealis Awards website:
The Sara Douglass Book Series Award is named for one of Australia’s best known speculative fiction writers. Sara Douglass was the flagship author of the HarperVoyager Australian line, which launched the careers of many of our most popular writers, and paved the way for the vibrant and diverse speculative fiction scene Australia has today. Sara’s contribution to the state of speculative fiction in Australia cannot be underestimated, and we are proud to commemorate her in this Award.
For more info head to their website here.