I'm trying to print a set of JSDOC tutorials as a book.
This works quite well but for the fact that table layout
of a table produced inside Markdown has no
gaps between columns.

Not insurmountable to fix in CSS, but...

Indeed, quite doable in CSS. E.g. with something like:

th, td { border-right: 1em solid white }

There is also the border-spacing property on tables.

“The advantage of a bad memory is that one enjoys several times the same good things for the first time.”
― Friedrich Nietzsche