There are many good Italy guidebooks to choose from. Here are a few we like:
Blue Guides: Paul Blanchard, Northern Italy, Norton, 12th ed., 2005
[Also Concise Italy, Central Italy, others, 2009]
Dry to some, but easily the most serious, detailed guides to the art, architecture and history. Maps of all the major towns, good practical info, no photos.
Eyewitness Travel Guides: Adele Evans et alia, Italy, DK Publishing, 2012
[also Florence & Tuscany, Milan & The Lakes, others]
Very popular guides, well laid-out, heavily illustrated. They also publish good Top 10 guides.
Fred Plotkin, Italy for the Gourmet Traveler, Kyle Books, rev. ed. 2007
Henry James, Italian Hours, Penguin Classics, 1995 (orig. 1909)
Mary McCarthy, The Stones of Florence, (orig. 1959) & Venice Observed, (orig. 1956), Penguin, 2006
Tim Parks, Italian Neighbors, Grove Weindenfeld, 1992; An Italian Education,
Avon Books, 1995
Julien Budden, The Operas of Verdi, 3 vol., Oxford, rev.ed. 1992 Detailed musical analyses.
Mosco Carner, Puccini: A Critical Biography, Knopf, orig. 1959 Long the standard bio.
Earl of Harewood and Gustav Kobbé, The New Kobbé’s Opera Book,
Putnam, 11th ed. (1997)
Mary Jane Phillips-Matz, Verdi: A Biography, Oxford, 1996 (orig. 1993);
Puccini: A Biography, Northeastern, 2002
Well researched, exhaustive, and perhaps definitive bios of the subjects.
Luigi Barzini, The Italians, Atheneum, 1996 (orig.1964)
Harry Hearder & Jonathan Morris, Italy: A Short History, Cambridge, 2nd ed., 2001
Peter & Linda Murray, Art of the Renaissance, Thanes and Hudson, 1985
Ross King, Brunelleschi’s Dome: How a Renaissance Genius Reinvented Architecture, Penguin, 2001; Michelangelo and the Pope’s Ceiling, Penguin, 2003
Stendhal (Henri Beyle), The Charterhouse of Parma (1838) trans. Howard, Scott-Moncrief
George Eliot, Romola (1863) A historical novel of Renaissance Florence.
Henry James, The Portrait of a Lady (1881) The Old World meets the New.
E.M. Forster, Where Angels Fear to Tread (1905); A Room with a View (1908)
The English learn how to live from life in the south.
Giorgio Bassani, The Garden of the Finzi-Continis (1962)
A haunting story of Fascist Italy and a family of upper class Jews in Ferrara.