That Joker graphic novel was way more hardcore than I thought it would be. I didn't expect to see some of the things I saw in that book.
Geoff Johns' Green Lantern stories are really good, especially Sinestro Corps War Green Lantern: Rebirth Green Lantern: Sinestro Corps War Vol 1 & 2 Mark Waid's Flash stories are also really good, such as Return of Barry Allen, Terminal Velocity, and Dead Heat. Dan Jurgen's Death and Return of Superman stories are good, too.
I loved Jim Lee's artwork and his rendition of Batman, but I didn't care that much for the story though. I loved Identity Crisis. Elongated Man's story continues in 52, so check out that 4 volume story arc also.