It's hard to pin down what's up with love in Cat's Cradle. (We're sure there's a lepidopterist joke we can make here, but we just don't have the heart.) The love between Mona and John is definitely an illusion, no qualms about it. But the Mintons form what John calls a duprass, a karass of only two people. That love be real, yo. To further complicate things, Newt's love for Zinka was completely and totally on the up-and-up, while her love for him seems to have been a lie staged to get his ice-nine. So, in the end, we can't say definitively whether Cat's Cradle sees love as real, an illusion, or something in-between. All we can say is that, either way, it suggests love is something worth having.
Love in Cat's Cradle is grouped with such human endeavors as art and religion: it's ultimately a lie, but a good lie, the kind that helps you make it through your day.
In Cat's Cradle, love is only decent when it's directed at other people. All instances of love directed at institutions such as science and nations are viewed as twisted—with the possible except of art.