Wide table to narrow table

[Rich Shepard]

My book has many tables that are very wide and have only a few (3-4) rows.
They fit on a page in landscape mode but don't look attractive as a narrow
vertical strip in the center of the page.

I want to reformat these tables so they have fewer columns and more rows;
that is the number of columns are divided in half with the right-most
columns underneath the left-most.

Double lines in tables should be avoided so I'm asking for ideas that would
produce attractive table layouts across the width of the text area in
portrait mode rather than a thin strip in landscape mode.

TIA,

Rich