Good grief, it’s a classic!

Does anyone remember the original “Joy of Sex” book? My parents had a hard copy, big thick book, white cover with gold writing, hidden in the cedar chest. Any ways … I was in an old book store and found this same book. When I opened it up, all the illustrations were coloured over in black. I asked the book store owner if he knew this book was like this. He told me that all copies of this book were to be blacked out because some law is saying it was pornography. Has anyone ever heard about this ? Blacking out certain pictures/ illustrations before being sold in seconds hand stores ? I think every parent back in the day had this book. It’s a classic!!