Invoice books

How are invoice books made? I have been researching the types of printers I would need (as explained in previous post) and I found that to print on NCR you need an impact printer. This makes sense since it's the impression that transfers the writing onto the other page(s). After further digging I found that they can be printed on laser printers. If doing them this way are they printed each individual page at a time (white, yellow, then pink)? Do you need to then glue the pages together? Then glue them in to a book with the cardboard (or staple them like some places do)? Can you buy them preassembled to run through an impact printer then do the perforation? Or do they come as individual sheets? Which way does everyone use?