I can recommend David Gilmour's The Pursuit of Italy. It's a pretty expansive but really well-written and contemplative account of the historical drives behind the Italian Unification.

Two books that are intended as introductions to the Risorgimento are Risorgimento: The History of Italy from Napoleon to Nation State by Lucy Riall and the second edition of The Risorgimento and the Unification of Italy by Derek Beales. Both books are roughly chronological surveys of the various steps towards Italian unification.

I would also recommend the novel The Leopard by Giuseppe Di Lampedusa and its 1963 film adaptation directed by Luchino Visconti. Lapedusa was a Sicilian aristocrat and his novel explores the cultural world unification interrupted and transformed. The film adaptation, directed by a homosexual Northern Italian communist aristocrat (yes, you read that correctly) adds an interesting perspective on unification's compromised nature and the ultimate betrayal of its ideals.