It's a line aimed at young adults and mature readers similar to early Vertigo. All are set in the DC universe.
Doom Patrol is a pseudo-continuation of Grant Morrison's Doom Patrol, which was essentially what birthed Vertigo. You don't need to have read Morrison's run but it's one of those comics everyone should read anyway so I suggest you do.
Cave Carson Has A Cybernetic Eye is similar in concept to Morrison's Animal Man: take a character no one has used in a long time and do a "where are they now?" type of story.
Mother Panic is about a vigilante in Gotham but who isn't related to Batman in any fashion.
Shade the Changing Girl is a pseudo-continuation of Peter Milligan's Shade the Changing Man, another early Vertigo landmark. Like Doom Patrol it combines new characters with existing ones and doesn't have a direct story connection to its predecessor, but it uses similar themes and makes references to it.
Bug! The Adventures of Forager is Lee, Michael and Laura Allred's tribute to everything Jack Kirby. It uses one of the most obscure New Gods characters and is all about the most obscure Kirby classics there are, including his versions of Sandman and Manhunter and even a couple of Blue Beetle newspaper strips he did uncredited.
Currently still uploading so wait a few minutes before downloading:https://www.dropbox.com/sh/q9yc30qqd0ibw3o/AADFlCzlQtfCEFIecbCXn9Z-a?dl=0>>94342070
Honestly I can't blame them. The books are meant for the book store market, not the floppy buying one. Bug especially is aimed at a VERY specific kind of extremely hardcore fan.