Note: Import and Export used in this discussion prior to my post, was using the Tool on the Library Icon, which bundles all pices into a easy to use package.
Prior to this, you had to copy each and every Library (if more than 1), copy the configuration folder. To restore: you had to put the pieces into their proper places (and adjust locations if needed)
The last suggestion by eschwartz (if I read 'Import' right), was to RECONSTRUCT from just book files, using Add Books. This is tedious
and IMHO a last resort
Don't wipe drive on old computers... Remove them and Keep them (label where they came from) to be installed in a USB drive caddy or as a Second Internal drive if you have a Desktop. The new owner can buy a NEW drive for a pittance