Preheat oven to 350F. Add olive oil and garlic to a small bowl.
Slice the baguette into 12 approx. 1/2" slices. Arrange them on a baking sheet. Brush the olive oil and garlic mixture onto both sides of each slice. Bake for 10 minutes.
Meanwhile, add the balsamic vinegar and honey to a small pan. Cook it on medium-high (reduce to medium if it's furiously bubbling) for about 8-10 minutes, or until the mixture easily coats the back of a spoon. It tends to thicken up more as it cools, so make sure you don't overdo it or you'll be left with a stuck-on mess. Set aside.
While your balsamic reduction is cooking, you can slice the tomatoes and chop the basil.
Set your oven's broiler to high and move the rack to the top third of the oven. Add a mozzarella slice to each piece of bread. Broil for 5 minutes or until the cheese melts (watch it closely), taking care not to burn the bread.
Top the crostini with the tomatoes, basil, a drizzle of the balsamic reduction, and some salt and pepper. Serve immediately.