I think your goal is unrealistic. If you're going to categorise books (and personally that's something I've never felt any urge to do), then many books do fit into more than one category. Eg Asimov's "Caves of Steel" has to be categorised as both "Crime" and "SF". Andy Weir's "The Martian" has to be "SF", "Mystery" (it's basically about solving puzzles) and Thriller" (it's certainly thrilling!).
Categories such as "SF" and "Crime" are orthogonal, not mutually exclusive.
I'd either accept that, or give up on your categorisation.
Last edited by HarryT; 10-18-2017 at 08:04 AM.
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