The series starts on the Enterprise with Data, Riker, Dr Crusher, Tasha Yar and others. The book (and the whole series) is about a virus that is very deadly and in this case it only kills people of mixed race. So racism against mixed people and people from other planets is a very big topic here which mixed with the virus topic actually is pretty close to our current situation here in Europe (speaking March 2020)... It shows that there are so many prejudices and hate for no reason and the people of all species are the same in one point: when it is about their life most of them are selfish idiots but there are always some who are willing to give all to help the ones in need. And this are the people that count!