A woman of her times and class, Lady Mary is in many ways bigoted or blinkered, but she is also open-minded, uninhibited, and above all curious about the world around her. She may have polished her letters to improve them, but she doesn't invent stories or pass off hearsay as fact, as did some of the guidebooks she had available.
She can write about dress styles and fashion to some correspondents, about antiquities and architecture to others, and exchange verses in Latin with Alexander Pope (with whom she later had a bitter falling-out). She writes about smallpox inoculation (which she used on her own children and later helped introduce to England), Turkish poetry (which she learned Turkish to better appreciate), historical sites, the workings of status and power at a personal level, and all kinds of other topics.
A thirty page introduction by Anita Desai gives a brief biography of Lady Mary, and for the modern reader the interest of the letters is as much in her character as in the places and people she describes. She was constrained by her social world — she apparently had to learn Latin in secret as a child — but her life still illustrates the confidence, arrogance and idiosyncrasy of the early modern British aristocracy, secure in their wealth and power and liberties.