Attack on Titan volumes were eight of the "Top 20 Adult Graphic Novels" sold in the bookstore channel in June, based on this chart provided exclusively to ICv2.com by Nielsen BookScan, with the rest of the chart an eclectic mix from a variety of publishers.  The Attack on Titan showing was a record, with the previous high six volumes in the Top 20 last September.  And with another three manga volumes in the Top 20 (Naruto and One Piece from VIZ Media, and Sword Art Online from Yen Press), there were a total of 11 manga titles in the Top 20, a resurgence for the category, if a bit concentrated.

The appearance of Yen's Sword Art Online on the list is interesting given that Amazon has been intentionally delaying shipments on Yen titles and selling them at short discount (see "Marvel, Yen Caught in Amazon-Hachette Crossfire").  Barnes & Noble must be moving some books with its sale (see "B&N Selling Hachette GNs at 54-57% Off").

On the flip side of that coin, Marvel's X-Men: Days of Future Past turned up on the list after being absent in May, the release month of the movie based on the volume.  Amazon was shipping the title with a delay in May (Marvel is a Hachette distribution client), but was handling Marvels normally by the end of the month (see "Amazon-Marvel Truce?").  It may have been too late for Captain America: The Winter Soldier, which made one appearance in the Top 20 in April, but had dropped off in May and has not reappeared in June.

Titan Comics placed a title in the Top 20; its licensed title Dreamworks: Dragons:  Riders of Berk Vol. 1 came in at #12.

From Image Comics, all three volumes of Saga placed in the Top 20, vs. only one The Walking Dead.

Two Scott Snyder Batman volumes from DC and DK Publishing's Marvel Encyclopedia rounded out the group.
 

BookScan Top 20 Graphic Novels in June 2014
Rank	Title	Author	Publisher
1	ATTACK ON TITAN VOL. 1	HAJIME ISAYAMA	KODANSHA COMICS
2	ATTACK ON TITAN VOL. 2	HAJIME ISAYAMA	KODANSHA COMICS
3	MARVEL ENCYCLOPEDIA UPDATED AND EXPANDED HC	MATT FORBECK	DK PUBLISHING
4	SAGA VOL. 3	BRIAN K VAUGHAN	IMAGE COMICS
5	ATTACK ON TITAN VOL. 12	HAJIME ISAYAMA	KODANSHA COMICS
6	ATTACK ON TITAN VOL. 3	HAJIME ISAYAMA	KODANSHA COMICS
7	NARUTO VOL. 65	MASASHI KISHIMOTO	VIZ MEDIA
8	SAGA VOL. 1	BRIAN K VAUGHAN	IMAGE COMICS
9	ATTACK ON TITAN VOL. 9	HAJIME ISAYAMA	KODANSHA COMICS
10	THE WALKING DEAD VOL. 20	ROBERT KIRKMAN	IMAGE COMICS
11	X-MEN: DAYS OF FUTURE PAST	CHRIS CLAREMONT	MARVEL COMICS
12	DREAMWORK'S DRAGONS: RIDERS OF BERK VOL. 1	SIMON FURMAN	TITAN COMICS
13	ATTACK ON TITAN VOL. 4	HAJIME ISAYAMA	KODANSHA COMICS
14	ATTACK ON TITAN VOL. 10	HAJIME ISAYAMA	KODANSHA COMICS
15	ONE PIECE VOL. 71	EIICHIRO ODA	VIZ MEDIA
16	BATMAN VOL. 4: ZERO-YEAR--SECRET CITY HC	SCOTT SNYDER	DC COMICS
17	BATMAN VOL. 3: DEATH OF THE FAMILY	SCOTT SNYDER	DC COMICS
18	ATTACK ON TITAN VOL. 11	HAJIME ISAYAMA	KODANSHA COMICS
19	SWORD ART ONLINE: AINCRAD	REKI KAWAHARA	YEN PRESS
20	SAGA VOL. 2	BRIAN K VAUGHAN	IMAGE COMICS

For past BookScan Top 20 Graphic Novel lists, see the "BookScan Top 20 GNs Index."