I didn't know what to do. I don't want to be responsible for ruining some writer's career. Since a year has gone by since you discovered what appears to be plagiarism, your options may be limited. Here are some points to consider, however, in making your decision. Let's think about this.
Plagiarism is theft .
It is not research, it is not a shortcut to getting ahead or getting published. It is theft, plain and simple. It is not an act deserving of sympathy or respect. That's a more difficult question. Whether it is worthwhile to do so is another question, however.