The Yin-Yang motif for the cover design of The Party Line was designed by me and created by a young artist by the name of Mina Schwind. I think she did a great job.
The bird in the Yin half of the circle is a phoenix and the Yang animal is a dragon. The phoenix symbolizes the reemergence of the human spirt, arising from the ashes of global suffering. The dragon represents chaos and discord. The idea being conveyed here is that the spirit and love is in an eternal juxtaposition with chaos and hate, with ebbs and flows between them, but with a sort of equilibrium when viewed from the perspective of eternity.
Please feel free to read the book for more on this.