IDW Publishing Comics- Ghostbusters Volume 9 (also known as Ghostbusters- Mass Hysteria! Part 2) is a trade paperback collection published on December 10, 2014. It features a cover that connects with the cover of Volume 8 to form one image, a forward by Jennifer Runyon, covers spread throughout the trade, variant cover art gallery, and a 30th Anniversary advertisement for previous volume trade paperbacks and omnibus editions of Ghostbusters Omnibus Volume 1, The Real Ghostbusters Omnibus Volume 1, and The Real Ghostbusters Omnibus Volume 2.
This trade paperback collects:
The original cover features:
- Ghostbusters: Kylie Griffin, Ray Stantz, Janine Melnitz, and Egon Spengler
In the background are:
- Gozer in first form, Louis Tully, the Stay Puft Marshmallow Man, Mot, the Ghostbusters II logo, Temple of Tiamat, and part of Ecto-1b.
Art from Volume 2 Issue #17-20 are reused several times for this trade collection:
- The first page is a reuse of Issue #17, page 16, panel 3
- The title page is a reuse of Issue #20, page 8
- Pages four to five reuses Issue #13, page 18, panel 5 and the Story so far from Issue #17
- Page 27 reuses Issue #17, Page 8, Panel 1
- Page 49 reuses Issue #18, Page 10, Panel 3
- Page 71 reuses Issue #19, Page 12, Panel 1
- Page 107 reuses Issue #20, Page 21, Panel 3
- The back cover is reuses Issue #20, Page 26
On September 25, 2014, Erik Burnham confirmed Jenny Moran's absence in Issue #20's conclusion was an oversight. She was meant to be mentioned in Ray's entry. It will be corrected in the Volume 9 trade paperback. 
- The Diamond order code is OCT140469.
- Every cover from Issues #17 to #20 appears in the trade except for the Issue #17 subscription cover featuring the Angry Birds theme.
- On the first panel of page 17 of the Issue #20 section, the swapped word balloon error is fixed.
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