My mother is a full blooded Italian and she also runs a restaurant. As you might imagine, her cook book collection is extensive.
I've found Mario Batali's books to stay true to the authentic Italian cooking. His dishes are relatively easy to prepare and very very good. I've been cooking out of his Italian Grill cookbook that was released not too long ago, I've been more than satisfied with the results. It might be cliche since it's Batali but he is extremely authentic. Read "HEAT" by Bill Buford, it's about Batali and Italian cuisine.
Christina's of Sun Valley - she is Italian and runs a small upscale italian restaurant. Her book as well is VERY authentic and I LOVE IT! Boar, Lamb, Poultry, Risotta, Homemade Pasta's, Gelati, Sorbetto, it's all there - I've tried all sorts of new dishes and i've been very happy. This is one of my mom's favorite new recipe books.
I'll go through my mom's collection at work tomorrow, there are two cookbooks she has that are probably 20 years old, that might still be in production. They are as authentic as it gets - from curing meats, pasta doughs, techniques, to game meat, and seafood. It's a really neat book.