I believe I first encountered Cooke’s drawings when reading Catwoman: Trail of the Catwoman by him and Ed Brubaker. They were quite unlike anything I’d seen before: smooth and angular, similar to Bruce Timm’s work on the DCAU, but different. He drew everything as if they came straight from the Golden Age, straight from the 1940s and ‘50s. Wavy haircuts, men in business suits, women in beautiful dresses or in sharp outfits themselves.
If you have a chance to read DC: The New Frontier, please do so. It basically posits a world where the DC Universe started in the ‘40s and everything progressed in real time, through the Red Scare of the ‘50s and the Nixon Era. At times, it’s depressing, but Cooke always knew how to bring back hope. And every image is infused with a level of care and detail you rarely see.
Cooke and artist J. Bone also did a series for The Spirit, which I think was the closest possible style and feeling to Will Eisner’s original.
There’s also Batman: Ego and Other Tails, a collection of his short stories and one-shots from Batman: Black and White and Solo.
The last comic he illustrated was The Twilight Children, written by Gilbert Hernandez (one of the “Love and Rockets” Hernandez Brothers). Even through each of the four issues, you could see the genuine care and artistry in each panel.
You can find a lot of his DC artwork in Graphic Ink: The DC Comics Art of Darwyn Cooke.