4.5, with the artwork bumping it up a lot for me - the full pages of this are incredible.
I had a chance in comparing the soft and hardcover, and went with the hardcover because i wamted it to open fully just for those full pages. The bits that are allowed more color (anyrhing D&D) are also beautiful.
The story is simple enough - letting you see the other side of what happens in the ST universe in season 1,that is, what will experiences in the upside down. For this reason, the target audience is limited to fans of the show; when can understand the story without it, but i don't know if it would remain as interesting