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That's disgusting. Who would treat unsold books this way?

That's what I initially told myself. But after seeing shelves after shelves of book covers vandalized, I hypothesized "What if the person who did this, is not a person?". It's hard to believe someone who has a bad habit of curling up soft cover texts, went through hundreds of books across different genres.

Then it struck my mind, it's rainy season in Bangkok, where this book store is located. This realization was the key to solving this book curling mystery.

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The key pieces of information were:
- It's rainy season in Bangkok
- The book store is situated in a top floor of a mall
- Books are made of dried paper
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I quickly pulled up my phone and googled "is humid air lighter than dry air?" Turns out it is, which means humid air actually travels upwards. Yes, the humid air rose to the top floor of the mall after heavy rain, and the air ventilation somehow weren't sufficient to keep the air dry in the book store, hence the result.