This is obviously a question that could have a lot of varied answers, but I think that Julia Alvarez has done a great job of proving that she is a novelist of literary merit. She has a unique and creative voice and is inventive in her style. Her two most famous novels are probably How the Garcia Girls Lost Their Accent and In the Time of the Butterflies. I will talk about the later novel a little bit as evidence of Alvarez's talent.
This novel is the story of four sisters who grew up under the dictatorship of Trujillo in the Dominican Republic in the 1950's and 60's. One interesting feature of the novel is that we are told in chapter one that three of the four sisters were murdered, and so we as readers have that knowledge from the start and then read the novel to find out what actually happened that led up to such an awful result. The story goes on to be told from each of the sister's individual perspectives. Each sister has her own chapters that are told in first person. It is so interesting to be that involved in the characters and to "hear their voices" as one reads the novel. It is especially interesting when each of the girls tell their perspective of a shared experience like what happens when they are imprisoned together.
Even though we know what happens to the sisters, Alvarez does an excellent job of creating suspense. As we see the sisters grow up and grow together in their fight against Trujillo, we wonder what will be the event that pushes Trujillo too far and what will push him to order their killing. Even though we know what will happen, Alvarez does a great job of still evoking our emotions and leaving us so sad that it had to end that way.
Alvarez does a wonderful job of creating a realistic sense of time and place and makes us cheer on the "Mariposas" even though we know it will not end as we would like.