Just reread Rebirth and liked it more the second time around, now thinking Geoff Johns is up there in the Moore, Morrison, Bendis, Ellis stratosphere. I stopped with Rebirth, but saw Blackest Night books in the book store and love the horror tone and artwork and am wondering if I should just jump over Sinestro Wars and the multiple other books right into BN. BN seems out of sequence across several volumes, so the question is if you wanted to catch up with GL fresh out of Rebirth on say only 3-5 GN, what is worthwhile and matches the depth and fire of Rebirth?
I would probably say Rebirth, No Fear, Revenge of the Green Lanterns, and both volumes of Sinestro Corps War are the best leading up to Blackest Night as these are really the books that introduce the War of Light and what have you. You might miss a little without Red Lantern and Agent Orange but nothing you can't catch up on easily.
if you only wanted to buy a handful of them, i would recommend both sinestro corps war volumes, agent orange, rage of the red lanterns, secret origin, blackest night green lantern, blackest night green lantern corps, and blackest night itself.
Just go to your local bookstore and read all the green lantern and green lantern corps trades in order from Rebirth through Blackest Night. You can tell which goes in order by looking at their copyright information inside the book and it lists which issue numbers are printed in the books. You will definitely need to read Sinestro Corps Wars and the following after before Blackest Night. The trades before Sinestro Corps Wars but after Rebirth and To Be a Lantern aren't completely necessary but I would read them anyway for more information on the Lanterns and stuff they've already gone through.