Do you say La adopción es ambos o ambas?

Do you say La adopción es ambos o ambas?
 

The author has the book titled Adoption is Both. She is referring to feelings from happy to sad to proud, anger etc not gender. The title is like a catch phrase.

The catchphrase should use 'ambos', since it ultimately refers to a concept. The reader will understand the concept the author had in mind while perusing the book, but certainly not at first, just as the English book title gives us no idea about the idea (concept).

Thank you!