Silver Age" was a twelve part storyline that ran through a series of one shot comic books published by DC Comics in 2000.
Each of the 12 issues were a one-shot (feature issue #1 on the cover), however they formed a larger story-arc in which The Justice League of America fights the Injustice League formed by villain Agamemno.
The art, dialogue, narrative style and even the format of the comics (larger page-counts, half-page advertisements, etc.) were deliberately anachronistic for the time of publication, thus the issues served as a tribute, and in some cases a gentle satire, to the books and creators of DC Comics during the Silver Age of Comic Books.