I'm trying to find a graphic novel about two kids, a boy and a girl, who moved to an old family house because they couldn't afford where they were living anymore. In the house, they discovered a doorway to another world, which they went through to have adventures. At one point there was a flashback showing how the kids' father died when the whole family was in the car. The car went over a cliff and they all managed to get out of it in time except the dad.
Most obvious thing I can remember is the purple tentacles coming out of the door on the cover. I'm pretty sure I also remember a talking bunny who flew some kind of ship and possibly had a big gun.
Ring any bells for anybody?
