The Main Series for the League of Extraordinary Gentlemen consists of 5 volumes created by Alan Moore and Kevin O'Neill lasting from 1999 to 2019. Due to its immense crossover nature, the series became a hit. Soon after publication of the first volume, a film adaptation was made in 2003. A new film adaptation was just announced.
In the video above, Alan Moore describes the process in which him and Kevin O'Neill created the series.