The book "Undatable" is displayed in the comedic section in the bookstore. It's only meant for a good chuckle or two.
Some real reasons that should make any guy undatable:
1. He's an abuser, cheater, liar, stealer
2. He has no respect for the person he's dating
3. Unemployed and no desire to get a job
4. Do drugs
5. Bad body hygiene
6. Ego maniac