One of the surprising things about your “novels of ideas” is that they work so well just as novels. I’ve heard people describe them as page turners.
Novels like Ishmael, The Story of B, and My Ishmael work as novels—and become page turners—because they were CONCEIVED as novels. They begin, as most novels do, with protagonists who have problems to solve—deep, important problems that are warping their lives—and you become involved in their struggle to solve them.
This is what separates these novel from a book like Ecotopia, which seems to me to be more a tract or instruction manual than a novel.