It is possible to overuse the well-turned fragment, but frags can also work beautifully to streamline narration, create tension as well as to vary the prose-line. A series of grammatically proper sentences can stiffen that line, make it less pliable. Purists hate to hear that and will deny it to their dying breath, but it’s true. Language does not always have to wear a tie and lace-up shoes. The object of fiction isn’t grammatical correctness but to make the reader welcome and then tell a story… to make him/her forget, whenever possible, that he/she is reading a story at all. The single-sentence paragraph more closely resembles talk than writing, and that’s good. Writing is seduction. Good talk is part of seduction. If not so, why do so many couples who start the evening at dinner wind up in bed?