Saffy's Angel by Hilary McKay
Saffy's Angel was the winner of the 2002 Whitbread Award and is the first novel in Hilary McKay's hilarious Casson Family series.
After Saffron discovers that she's adopted, life is never quite the same. Her artistic parents and doting siblings adore her, but Saffy wants a piece of her past. So when her grandfather bequests her a stone angel - a relic from the childhood she never knew - Saffy knows she has to find it. Realizing that Siena holds the key, she stows away on a car trip to Italy.
The rest of the family are engaged in their own wacky projects: Caddy, a hopeless student, is revising for her A levels and desperately trying to pass her driving test. Indigo, the only boy in the Casson family, is determined to rid himself of his fear of heights. And the youngest, Rose, a budding artist, has a knack for baiting her pompous dad, with entertaining results . . .
Follow the family's adventures in the rest of the beloved series: Indigo's Star, Permanent Rose, Caddy Ever After, Forever Rose and Caddy's World.