THE SEVEN DEADLY SISTERS by Pat McGerr                       STAIRCASE 4 by Helen Reilly                                                     Dell Books, 1st Paperback Printings, 1950 & 1951                       Condition: Good+                                                                                                                                                                               Two vintage Dell mapback mystery novels by women, one an award- winning author, the other a former president of the  Mystery Writers of America.  Both books have  spine leans, front cover corner creasing, spine edge wear, light page toning.  SISTERS has a short spine end tear,  but no writing. STAIRCASE has more significant lower spine end tears, small writing on front cover & title page.   But both have secure bindings.