The leftovers of several Batman adventures combined in a volume.It was a weird idea because the stories in the volume are unstable.Some are great, some are good and some are mediocre.In the end graveyard shift feels like a emotional journey through different parts of Batman's life.

In Short: Skip this one, you wont be missing anything.

Collects a handful of random issues that didn't make it into the "Zero Year" series, as well as a few issues from other Batman runs. (Batman Eternal, and I think Batman Inc.) The individual stories themselves are fine, but un-extraordinary. The fact that this is such a disjointed collection of stories, across several different runs is my issue with it. It's filler. It doesn't progress the "Batman" narrative in any significant way shape or form.
It's a cheap cash-grab. Wait for Endgame.