He has had a passion for reading since he was young.
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usage
嗜 implies an intense, often excessive fondness. Common compounds: 嗜好 (shìhào, hobby/addiction), 嗜血 (shìxuè, bloodthirsty), 嗜酒 (shìjiǔ, alcoholism). It carries a stronger connotation than 喜欢 (xǐhuan, to like).
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嗜 is literary and formal. In casual speech, people would say 特别爱 (tèbié ài, really love) or 上瘾 (shàngyǐn, addicted) instead.