Worth while

Overworked as a term of vague approval and (with not) of disapproval. Strictly applicable only to actions: “Is it worth while to telegraph?”

Poor: His books are not worth while.
Better: His books are not worth reading (not worth one’s while to read; do not repay reading).

The use of worth while before a noun (“a worth while story”) is indefensible. 

From: William Strunk, Jr., The Elements of Style, 1918.