You should part it out and sell me all of the hardware. I've got a 60s EB-2 copy that needs a new tailpiece.
I kid, I kid...
Without photos, it's hard to say whether or not it will get worse, but these hollowbodies are prone to this kind of problem, so it's a common repair. And from what I read, it should be an easy one. I would head to Home Depot and get a small bottle of wood glue (I like TiteBond II).
Mask off the sides and back where the back is lifting. and squeeze a bit of glue in between the two, along the entire length of the gap. Now, unless you've got some clamps, you'll have to hold the back down to the side with your hands. Wipe away any excess glue and hold it in place for at least 30 minutes (longer, if it's cold).
After that, the glue SHOULD be set, but its not going to be ready to handle for another 24 hours. Lightly sand the seam and finish cracks with a fine grit sandpaper (at least 220p) and go over it with clear nail polish. If you don't have any, super glue will also work.
