Know this is late but here are a few I've read:
Infidelity on the Internet: Virtual Relationships and Real Betrayal by Marlene M. Maheu & Rona Subotnik.
Topics include:
- Love at the Speed of Electricity: The eleven types of cyber-lovers
- Cyber-Romance: Why people seek it
- Cyber-Sex: Types of cyber-sexual activities, including chat room, MUDS, private cameras and erotic stories
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Love Online: Emotions on the Internet by Aaron Ben-Ze'ev
"How is an online affair where the two people involved may never see or meet each other different from an affair in the real world? Does online sex still involve cheating on your partner?"
Hope these help 
