Use standard library catalogs to tag, integrate tag search (Unity Lenses, FileMgr). Use file content to assign many tags.
Use standard library catalogs to tag file based on file content, integrate tag search (Unity Lenses, FileMgrs.) into Operating System. Re-organize files into sub-folders as in Libraries for public data.
Actually, there is nothing to do manually for books - all tags should be assigned automatically. All book (data) related info from Wikipedia, WikiMedia, the Time, Epoch, other writers, scientists, other cross-reference data may be available for review also.

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Oleksandr commented
Also, I would like to have much more tags and filename is not the best place to store them. Sort all public files, find content duplicates based on tag info (pdf, djvu, fb2, epub), etc. Statistics for most unique words to identify first and then assign tags. Keep strong folder organization in NAS and prevent file dropping everywhere.
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Oleksandr commented
use tag rating to improve public tag catalog