Yes. It's a technique that's been used many times. As the story is actually something that has happened sometime in the past, these are quotations from reports, scientific papers, memoirs, etc., that deal with the phenomenon. The Shadow Exploded is an examination into the causes (physical and societal, as I recall, though I've not read Carrie in a very long time) behind the disaster. And, as such a case would be unprecedented -- this powerful a telekinetic outburst, one that decimated an entire town -- it is also trying to come to grips with rewriting the way human beings look at things -- if such things are real, there's a desperate need to understand them in order to control or contain them, lest the experience be repeated, who knows how many times.
So, King presents you with the papers done on this in the present-day, interposed with telling the actual events as they unfolded, building up to the crisis point. The thing that make this technique so important in this novel is that Carrie is not an isolated case -- or they fear she's not -- and therefore, by inserting these excerpts from these documents, he's already foreshadowing the fallout -- a fallout that extends far, far beyond the community that Carrie devastated, into the world at large.
