Well, the technothriller is first a thriller, then a technothriller. It thrills the reader. The pace is fast and unrelenting. Thrillers also have a sense of urgency that demands that they be finished. When someone tells you about starting a book and being unable to put it down, most likely the book is a thriller.
Thrillers are one of the most popular forms of fiction.
They can be science fiction, mystery, suspense, or westerns and still be thrillers. The genre isn't important. What makes a book a thriller is the pace and urgency of the novel. Thus, World War novels about secret death rays or new airplanes were the technothrillers of their time. So, the technothriller must be a pretty recent innovation.