Borderlands 3 is hitting Steam in just two days on March 13th and if you've been waiting until now to pick it up, this is your best chance to do so. From now until March 20th (so technically you don't have to pre-order it) all three editions are on sale for half off. These include the standard edition for $29.99, the Digital Deluxe Edition for $39.99 (this includes a lot of cosmetic items), and the Super Deluxe Edition for $49.99 which includes the content from the Digital Deluxe Edition as well as the Season Pass which nets you four DLC packs and the Butt Stallion cosmetic pack.
If you're looking to check out the previous games in the series, then you might want to look into the Borderlands Bundle. Once it launches (there's no specified date but it'll presumably launch when Borderlands 3 launches on Friday) this bundle will contain everything Borderlands that's been released from Borderlands: Game of the Year Edition, Borderlands: The Handsome Collection, and Borderlands 3 (Borderlands: GOTY and Borderlands: The Handsome Collection will have all DLC with it, Borderlands 3 looks to just be the base game). All of it for only $60.90. That's 81% off the regular price of almost $320. However, I didn't see a date for when that offer ends so if you're looking to fill out your Borderlands library on Steam, now's the time.