By Sid Perkins
Skeleton Keys
Brian Switek
Riverhead Books, $26
At this very moment, voracious cells are eating away at your bones. Not to worry, though — that’s just a normal part of bone maintenance in healthy adults. The formation of new bone cells balances out the removal of old bone cells. Although bone-making cells rev up when a bone breaks or disease sets in, eventually bone-eating cells kick in to make sure a bone doesn’t grow out of control. Bones as active tissues, not fixed structures, is just one of the fascinating topics that writer Brian Switek explores in Skeleton Keys.