How to draw a horizontal line in flutter row widgets?

Try wrapping you Column in an Expanded so the Divider knows how much space to occupy.

Container(
  color: Colors.white,
  child: (Row(
    children: <Widget>[
      // ...
      Expanded(
        child: Column(
          children: <Widget>[
            Text("Book Name"),
            Text("Author name"),
            Divider(
              color: Colors.black
            )
          ],
        ),
      )
    ],
  )),
);