Not very different from today in that it was highly regional. On the coast, you see lots of seafood dishes. Near the Alps hearty stews and meat pies have remained largely unchanged in 600 years. Tomato use is widespread now, of course, and every Sunday my Italian friends all retreat to their family homes to cook ragu, but the other dishes on the table would be perfectly familiar to a 14th century Italian.

Many old cookbooks have been scanned and translated online. They are great fun to read and I have participated in groups that recreate some of the dishes for themed pot lucks -- if you are motivated, consider finding a local medieval cooking group!

Here are some translated recipe collections that illustrate my points:

http://www.medievalcuisine.com/Euriol/my-recipes/recipes-by-time-period/14th-century

http://www.medievalcuisine.com/Euriol/my-recipes/recipes-by-time-period/15th-century

The rightmost column shows the original source. Scanned copies for 90% of them are free on Google Books or Project Gutenberg.

And a collection of these and other recipes adapted for the modern kitchen:

http://www.godecookery.com/gcooktoc/gcooktoc.htm

If you're looking for a modern history, I can vouch for The Oxford Companion to Italian Food (ISBN 0198606176) and The Medieval Kitchen: Recipes from France and Italy (0226706850), as they both draw heavily on the previously linked cookbooks and explain the history of each dish.

As you read through the recipes, you can see that all of the spices are still in a modern spice rack. Cinnamon, honey, salt, pepper, ground ginger, fennel...