In a food processor or a zipped-top bag with a rolling pin, crush the graham crackers into fine crumbs. You may need to do this in batches.
1 (14 oz.) box graham crackers
In a large bowl, combine the graham cracker crumbs with the melted butter and stir until evenly combined.
3/4 cup butter
Spray a 9x13-inch baking dish with nonstick spray. Press half of the graham cracker mixture firmly into the bottom of the dish to form the crust, using the bottom of a measuring cup to pack it down tightly.
cooking spray
Place the dish in the freezer for at least 30 minutes to firm up the crust.
In a medium saucepan over medium heat, combine the blueberries, 1/2 cup of the sugar, water, cornstarch, and lemon zest. Cook, stirring constantly, until the mixture thickens. Remove from heat and let cool completely.
3 cups blueberries, 2 cups granulated sugar, 2/3 cup water, 1/2 cup cornstarch, 1 tbsp. lemon zest
In a large mixing bowl, beat together the softened cream cheese and the remaining 1 1/2 cups sugar until smooth and fluffy.
16 oz. full-fat cream cheese
Use a rubber spatula to gently fold in the thawed Cool Whip until fully incorporated.
1 (8 oz.) tub Cool Whip
Once the crust is firm, spread half of the cream cheese mixture evenly over the crust.
Spoon the cooled blueberry mixture over the cream cheese layer and spread it gently to cover.
Top with the remaining cream cheese mixture and smooth it out evenly.
Sprinkle the remaining graham cracker mixture over the top and press it lightly into the cream cheese layer.
Cover and refrigerate overnight to fully set. Slice into squares and serve cold.