"Countdown" consists of 51 issues, number in reverse, published weekly for one year, crossing over with noteworthy and significant titles published by DC. The series covers much of the fictional DC Universe, told in parallel narratives, through the interconnecting stories of a cast of characters, and frequently crosses over with various other DC titles. Unlike the "52" limited series of the previous year, "Countdown" is not depicted as taking place in "real time" but presumably operates on the same floating timeline as DC Comics stories in general.