In the Confessions of a Shopaholic superstar’s latest lighter-than-a-champagne- bubble caper, Twenties Girl, young Londoner Lara is haunted by the ghost of her great-aunt Sadie. The feisty, Charleston-dancing flapper can’t go on to her final resting place until she finds her missing talisman, a glass-bead necklace. Kinsella writes with an ingratiating, breezy Brit wit, but in order to stretch the mystery over 435 pages, she forces her heroine to be bumbling, hysterical, and at times gratingly dense. The development of the unlikely friendship between a twentysomething urbanite and a ’20s-era phantom fares much better, in the end, than the clunky plot machinations. B?