The one that started it all. Batman focuses on the rise of the famous Batman and his influence on Gotham City as he fights the most devilish of villains and stops the most dastardly plans. It spanned from 1940-2011.
From Batman #343 storylines ran in both Batman and Detective Comics - this continued for 3½ years, those issues of Detective Comics are included in this collection.
Also worthy of mention is the original Batman collection from joshua13 - comprised solely of the scans available at the time, that torrent form the starting point for this 'digital update'.