Condition grading used books without a chemistry degree

The price sticker is the easy part. Whether a book can be sold as "very good" is where the craft lives.

Six checks we run over every used arrival, learned from a decade of customers opening the cover right in front of us:

1. The smell test. Musty means mildew, and mildew spreads to the shelf. A book that smells like an attic gets quarantined outside, full stop.
2. Spine crease economics. One soft crease adds character on a paperback; a cracked spine halves the price. Open it 30 degrees and watch the glue line.
3. Highlighting tolerance. Yellow marker on page 12 is "read". Every page highlighted is "loved", which is not the same as sellable.
4. The dust jacket arithmetic. A jacket in poor shape minus a €4 protective sleeve plus one evening equals a book back on the shelf at full grade. Worth it above roughly €8 used value.
5. Ex-libris or inscription? A neat 1970s gift inscription is provenance. A rubber stamp from a defunct lending library is... also provenance. We charge more for the first.
6. Page-hold test. Stand it up by the covers. If it fans open like a peacock, the binding is done — recycle or craft pile.

None of this needs instruments. It needs ten honest seconds per book and the discipline to say no to your own optimism. What does your shop do differently?