I'll provide pics later, but I wonder if it's time to add a Book style case as it seems they're becoming a little more popular. I've seen it a few times with Rome: The Complete Series (Blu-ray), Spartacus: The Complete First Season (DVD and BD) and now the Alien Anthology (BD).

Looks like a variation of a digipak... so that is what I would use.

Quoting Shumway Inc.:

Quote:
hey guys...i've got a new box set...but i'm not sure which kind of case type should i use for child profiles?
it has definitely a slip cover...

here some pics:

Actually, this is a Digistak.  It is a case type that needs to be added to the list.  I think, for now, "Custom" would be appropriate, like Silence says...

Technically, this is a Digistak®



Digistak® is a multiple disc packaging solution which consists of a rigid stack of trays, glued to a high quality cover of folding or rigid  cardboard or any other required material - combining functionality with excellent opportunities for design and special finishing.

The Digistak® layout is similar to the spine-binding system employed in books. With the discs 'stacked' in plastic trays rather than folded out, this patented system allows consumers to easily flip through the stack of discs as if they were paging through a book. The Digistak® can hold collections of 2 to 12 discs.

This is a DVDigipak®



Our DVDigipak®  is the Digipak®  specially developed for DVD sized discs. Functionality and perfect opportunities for design are offered for DVD projects, which require special packaging for one or multiple DVD discs. DVDigipak® combines the well-known characteristics of our Digipak® with the availability of special DVD trays.

This is a Digipak®



Digipak®. This sustainable media pack which consists of a cardboard base with one or more trays glued on the inside still excels in functionality and design opportunities.

The Digipak® can be supplied in standard formats such as the 4-12 pages, with tray(s) for CDs and sleeves or die-cut slots for booklets. This packaging can be used to incorporate pop-up messages and other special effects. Some of our special Digipaks are the midsize, the book size and the T-, L- and cross-form.

Mind you I'm talking about the trademarked descriptions

Charlie

I've got one I'm trying to classify.  It's for The Messenger, which until now has just been listed as keepcase, which is clearly wrong (I have a pending update adding actual coverscans, overview, and adding slip cover).  It almost seems to me like it's a digipak within a slipcase within a slip cover.  Here's a couple of scans of how it opens up...

Looks like 1 more dead tree to me. 

I have to agree... that looks just like another version of an envelope.

Quoting MakoDeth:

Quote:
I don't think it's a digipak as it seems to have no tray carrying the dvd glued to the cardboard... looks more like an envelope with slip-cover to me (comparing it with the first post in this thread)

Maybe your right.
It really looks more like an envelope with slip-cover.