I always loved when it would say "You bought No. 26 in a comic series, do you want No. 19 and 13?"
Yes, they're commonly bought together, but there's mostly, if not completely, a one-directional relationship-- someone buying 13 might want 14, 15, 16, but not the other way around.
This feels like it's just a matter of adding one more signed value to the "people who buy A buy B" record table... a weight indicating if the take is mostly A->B, B->A, or neutral.
Or, instead of the usual recommendation widget, just show a link to "All volumes in this series". Or even incorporate it into the website structure like YouTube playlists do.
Yes, they're commonly bought together, but there's mostly, if not completely, a one-directional relationship-- someone buying 13 might want 14, 15, 16, but not the other way around.
This feels like it's just a matter of adding one more signed value to the "people who buy A buy B" record table... a weight indicating if the take is mostly A->B, B->A, or neutral.