If you want to get a solid understanding of Green Lanterns and their universe, I’d recommend starting with "Green Lantern: Rebirth" by Geoff Johns. This 6-issue miniseries from 2004 revitalizes the character of Hal Jordan and re-establishes the Green Lantern Corps in a big way. It introduces key concepts and characters that are vital to understanding the entire lore, including the emotional spectrum and the various Lantern Corps.
After that, "Green Lantern" (2005-2011) by Geoff Johns is a great follow-up. This run delves deeper into the mythology of the Green Lanterns and includes essential story arcs like "Sinestro Corps War," which pits the Green Lantern Corps against former Green Lantern Sinestro and his yellow army. It’s packed with action and character development, making it a great read that balances continuity and lore.
I can’t skip mentioning "Blackest Night" (2009-2010) as an important arc, too. It expands on the emotional spectrum even further and introduces the idea of the Black Lanterns, raising the stakes for all the Lanterns involved. This event is a huge part of the overarching narrative, and it’s thrilling for both new and seasoned readers.
If you're looking for something more contemporary, "Green Lantern: Future State" is a recent storyline that features a new generation of Green Lanterns, including Jo Mullein. It showcases the evolution of the Corps and presents fresh takes on its legacy.
Each of these recommendations not only builds on the main characters and their motivations but also opens up the wider DC Universe in intriguing ways. Happy reading!