Big Boxes were similar to the packaging used for old CD-ROMS: Large boxes that opened at the top when you pulled open a tabbed flap, with the cassette resting inside a removable tray. Book boxes (larger than standard slipcases) opened, of course, like a book, with the cassette resting inside a built-in tray. Both were common in the 80's, but were phased out over time.
Book boxes should not be confused with clamshells. They're totally different. Book boxes are made of paperboard and do not snap shut. The cover is merely a flap of paperboard that opens on the right edge to expose the tape in its tray.
Thanks for considering. Also, please consider a better alternative to "cardsleeve" for LaserDiscs!
I agree on all points above