Personally, I don't use spread books, since there are really only a handful of basic themes, and everything else is mostly creative riffing on those themes. "Past/present/future" is the most obvious one, and all manner of imaginative hair-splitting goes on around that. Another one is the "focus-card-and-supporting-influences" theme, a third is the "dual-train" (and sometimes "multi-train") theme of comparative factors intended to support a decision of some sort, a fourth is the "yes/no" approach (which might be seen as a specialized case of the "dual-train" theme), and a fifth "catch-all" category would be the "developmental" theme (the Celtic Cross is one) that encompasses both timing elements and the evolutionary growth of a matter toward a particular outcome. Then there are the "pattern-based" layouts (stars, circles, squares, arcs, etc.) that don't have any intrinsic interpretive significance beyond being pleasingly balanced. There are also "psychological insight" spreads of different types ("thinks/feels" questions inspire a good many of them) but I don't use tarot for that purpose, finding astrology a much more effective tool for it. I'm not sure a thorough analysis has ever been done, but I would be surprised if there are more than a dozen or so "core" themes driving the thousands of different spreads out there.