This question shows up a surprising number of times.
A recent case from the Court of Appeals for the Sixth Circuit, Tomaydo-Tomahhdo, LLC, et al v. Vozary, Case No. 15-3179, Oct. 20, 2015 (not for publication), affirmed that, in that case, the recipes and the recipe book in question are not copyrightable. See Opinion (I am hosting a copy of the decision on Mega.co.nz).
The Court found that the recipes are not copyrightable. "The list of ingredients is merely a factual statement, and ... facts are not copyrightable." See Opinion at 5. Moreover, a "recipe's instructions, as functional directions, are statutorily excluded from copyright protection." See Opinion at 5.
Additionally, although recipe books can be protected as a compilation, the Court also found that this recipe book was not copyrightable. See Opinion at 6. The Court found that plaintiff-appellant never "point[ed] to anything to demonstrat[e] that the recipe book is an original compilation." See Opinion at 6. The plaintiff-appellant failed to identify the selection process for the recipes, what order to place the recipes, and how the recipes were arranged in the book. See Opinion at 4.
I believe the Court's conclusion that recipe instructions cannot be protected is overbroad. While I agree that the underlying process described in the instructions is not eligible for protection under 17 U.S.C. § 102(b), the description of the instructions may be eligible for protection. If you describe a instruction step with minimal verbage (e.g., "put egg in water"), then that description would not be eligible for protection. However, if you describe the instruction step with flowery illustrative verbage (e.g., "gently place the egg using a slotted spoon into the moderately boiling water using care not to immerse the egg to quickly"), then that original description should be eligible for protection. See U.S. Copyright Office, Compendium of U.S. Copyright Office Procedures, 3rd Ed. (Dec. 22, 2014) at § 716.