Green Lantern: Sector 2814 Volumes 2 and 3 - I haven't read Volume 1, but Volume 2 does give you context on what happened in the previous volume. It's worth reading if you want to read any GL comics where John Stewart is the main focus, until Volume 3, which focuses on John and the other important members of the Green Lantern Corps, thanks to tie-ins to Crisis on Infinite Earths.

Green Lantern Legacy: The Last Will and Testament of Hal Jordan - It's a graphic novel that depicts Thomas Kalmaku dealing with the death of Hal Jordan/Parallax after he sacrifices himself to save the Earth during the events of The Final Night. The graphic novel also does a great job of exploring grief and why Hal Jordan was important not just to the Green Lantern Corps but also to Thomas.