Hi VM44!
It's probably Loyd Berry, as the primary writer/editor, but most books have at least 2 writers. They take turns, one writes, while the other edits and fits the text to the allowed space. I recently called a friend of mine who was a "heavy" in writing (wrote many WT study articles, editor for FF, Aid book, and Insight...), and he indicated that he believed Loyd Berry was connected with it. Hope this helps. (If you need a more specific name, I can PM you.)