As a general rule, Never pick up, hold, or place (handle) a book by the spine side. As A GOLDEN RULE, NEVER handle a Stack of books by the spine. This is a sure-fire way to get those pesky, grade-dropping stresses and color breaks. All it takes is a single light pinch or squeeze and DINK!
I know it's almost impossible to think of it every time, but train your brain. And ask your LCS retailer to please handle the books by any side but the spine.
Also, carry a rigid brief tote or similar to tuck the books away in so there's no chance for disaster.
Carry on.