But your main point is that the publisher's rights to make money by printing a book I wrote is more important to preserve than the healthier (and tastier!) lives people will enjoy if I find it worth my time to write this book.
Yes. It is more important to have the massive long-term benefits of living in a society that can be relied upon to protect rights than the much smaller benefits of occasionally violating them.
Basically, libertarianism is inherently non-utilitarian. Am I correct?
In a sense yes and in a sense no. Libertarians won't compromise their values for short term utilitarian benefits because they believe it's to everyone's long term benefit not to do so. To use this example, sooner or later people probably will figure out his secret recipe, and with no IP, once they do so, they can spread it far and wide.
(Again, I think IP rights are real rights that Libertarians should expect governments to protect like all other rights. So I am not explaining my own position.)