Preheat oven to 375°F and grease a 9x13-inch baking dish.
In a large bowl, combine the squeezed-dry spinach, ricotta cheese, eggs, salt, pepper, nutmeg, garlic, and 1/2 cup Parmesan cheese. Mix until well combined.
Spread 1 cup of marinara sauce on the bottom of the prepared baking dish.
Layer 4 lasagna noodles over the sauce, spread with half of the spinach-ricotta mixture, drizzle with one-third of remaining marinara sauce, and top with one-quarter of the mozzarella cheese.
Repeat layers with noodles, remaining spinach mixture, more sauce, and another quarter of the mozzarella.
Top with remaining noodles, marinara sauce, mozzarella cheese, and remaining Parmesan cheese.
Cover with foil and bake for 45 minutes, then remove foil and bake an additional 15 minutes until cheese is bubbly and lightly browned.
Sprinkle with fresh basil and let stand for 15 minutes before serving.