The Blurb On The Back:
There is about 10 times more dark matter (DM, also known here as Alice matter) than bright stuff in our Galaxy.
The DM is spread out in a roughly uniform sphere (a spherical distribution of Alice stars), with our flattened disk Galaxy embedded in it. The “Alice matter”, is a kind of mirror image shadow stuff; the term “looking glass matter” has been used by some scientists. Alice matter can be turned into ordinary matter (and vice versa) by sending it though a loop of Alice string, a naturally occurring cosmic phenomenon.
Aliens in the DM world, more advanced than we are, have discovered the trace of 10 per cent “normal” matter in “their” universe. And have come to investigate it.
Our disk is a perturbation that they are puzzled about.
The Review (Cut For Spoilers):