In a large pot, cook pasta according to package directions, adding the shrimp the last 1 minute of cooking. Drain and return to pot.
Meanwhile, in a large skillet heat oil over medium heat. Add garlic; cook and stir for 30 seconds. Add spinach. Cook, tossing with tongs, for 1 to 2 minutes or until wilted. Remove from heat. Stir in lemon peel and juice.
Add spinach mixture to pasta mixture in pot. Toss to coat. Season to taste with salt and pepper. Drizzle each serving with additional olive oil, if desired.