This isn’t the first time that Richard LaGravenese, the gifted writer of A Little Princess and The Fisher King and writer-director of the lovely Living Out Loud, has gone best-seller slumming. His screenplay for The Bridges of Madison County was good enough to persuade a dispiriting number of respected critics that a movie was worth making out of that dreadful piece of pulp. Nothing, however, could redeem the chipper folk wisdom of P.S. I Love You, the first novel (for want of a better word) of Cecelia Ahern, a twentysomething Irish “writer” whose chief literary asset is a sharp eye for the winning romantic formula. Hilary Swank, who was not put in this world to simper, does little else as a young wife whose twinkly leprechaun of an Irish husband (Gerard Butler, who’s Scottish, but never mind) has died, leaving her to mope around in lacy black underwear, do her nails, and lean on Mom (Kathy Bates) and the usual wisecracking friends (Lisa Kudrow and Gina Gershon). Guided by flashbacks to happier days and perky letters left behind by her obliging hubby, Swank takes healing trips to scenic Wicklow County, where dimpled replacement hunks lie thick on the ground. LaGravenese has sliced away the worst of Ahern’s excruciating prose, but that proves a negative virtue. With “She longed for the couch to hold out its arms to her” out of the way, there’s little left to dance with but the old stages-of-grief two-step, and some blessedly irreverent noodling with Harry Connick Jr.