Child protection group NSPCC has slammed the publication, for sale on Amazon.com, which also argues that child abusers are not "monsters".
Paedophiles have posted reviews of the book - Understanding Loved Boys and Boylovers - on the website in praise of it.
One man said: "As a boylover, I found this book extremely helpful."
Publishers SafeHaven Foundation Press claim the book, by David L Riegel, is aimed at researchers and educators.
But Liz Atkins, NSPCC head of policy, stormed: "Sexual relationships between an adult and children must never be viewed positively.
"We know that sex offenders often look to justify their behaviour and any book that seeks to minimise the distressing and long term impact on children is unacceptable."
In the 108-page book, which has sold 150,000 copies, Mr Riegel describes paedophiles as "sincere, concerned, loving human beings" who have probably been born with "a sexual orientation neither understood nor accepted by most others".
Amazon said the book was not a child molester's "how-to", adding it had no role in censoring what it sold.