Melanie's Marvelous Measles was written to convince children and their parents that it's ok to not get vaccinated.
Here's the author describing it in her own words:
Melanie's Marvelous Measles was written to educate children on the benefits of having measles and how you can heal from the naturally and successfully. Often today, we are being bombarded with messages from vested interests to fear all disases in order for someone to sell some potion or vaccines, when, in fact, history shows that in industrialised countries, these diseases are quite benign, and, according to natural health sources, beneficial to the body.
Having raised three children vaccine-free and childhood disease-free, I have experienced many times when my children's vaccinated peers succumb to the childhood diseases they were vaccinated against. Surprisingly, there were times when my unvaccinated children were blamed for their peers' sickess. Something which is just not possible when they didn't have the diseases at all.