Author's first published novel.

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"It began on a summer's morning in July. The sun came up early in the morning mist, and the pavements were already steaming a little from the heavy dew. The air in the streets was stale and lifeless. It had been an exhausting month of intense heat, rainless skies, and warm, dust-laden winds"

Thus begins the the first published novel by which famous detective story writer. What is the novel called?