Under the Mountain

A 1001 CBYMRBYGU.
Rachel and Theo are twins, red-headed twins, and they are exactly what Mr. Jones has been seeking for so long. Jones needs the twins to save the earth from the enormous creatures that are preparing to turn the world into mud. Unfortunately, the twins are not identical, and this may destroy Jones' hopes for saving the world.

One of the things that struck me most about this book was when Rachel questioned Mr. Jones as to whether she and her brother must destroy the creatures, if it might be possible that the creatures could be reasoned with. That's unusual in a story in this genre.

Lots of action in this story. Lots of running and trying to escape from this slug-like space monsters. Lots of nervous and tense moments.