Veronica Sloan 
The Futanari Virus [EPUB ebook] 

A sensual mutation is transforming the women of Hapi, Delaware. As if by magic, their bodies are changing, gaining male anatomy in addition to their own! More aggressive, more powerful, and consumed by a passionate lust that borders on nymphomania, these frisky futanari cannot help seducing their friends and neighbors.
This erotic futa tale is 22, 000 words and recommended for adult readers.
~~~~~ Excerpt ~~~~~
"You keep staring at me, " Casey said.
Robin smiled. "Yes."
"What do you want to say to me?" Her slender finger drew a perpetual circle on the granite counter, that narrow lip between the sink and the cool air of the kitchen. "You saw me, didn't you?"
"When?"
Casey squeezed the lip. "Last Saturday. With Simon."
"Maybe."
A husky laugh cut its way through the girl's teeth. She panted for a moment, then rolled her fingers up her throat. She tried to loosen the sudden knot that had formed there, or identify the source of the heat. But it was fruitless. She reached back, to the tie that bound her hair, and pulled it loose. Her dark tresses skated over her naked shoulders. "You watched me."
"I did."
"How long did you watch me?"
"I watched the whole thing."
"Why?" She turned to Robin at last, and knew precisely why.
Neither woman knew why her body felt so hot, but they understood the sensation. Raw arousal was in the air, almost thick enough to taste. It emanated from Robin's pores and saturated the air that Casey breathed. Lust spread from her lungs to other sensitive body parts, until she was consciously squeezing her thighs together. She had felt this queer attraction the night before, when she smelled Robin's sweat, but ascribed it to the alcohol…
Simon had never looked at her the way Robin did now – the way, she realized, that the older woman had always looked at her. "Am I safe here?" she asked.
"I don't know, " Robin said.
"So I should say thank you and leave."
"Yes, " Robin said.
"But if I don't leave?" Casey squeezed the counter lip. "What will you do if I don't leave?"
"I'll tell you how to thank me."
Casey tugged at her hair, and bit her lip, and gazed down into Robin's piercing eyes. "How do I thank you?" she whispered.