Reddit mentions of The Nameless City

All Ages

• Fable Comics | Charise Mericle Harper
  
• Fairy Tale Comics | Telgemeier, Thompson, Mazzucchelli, et al.
  
• Guinea Pig: Pet Shop Private Eye | Colleen AF Venable
  
• Hilda and the Troll, Hilda and the Midnight Giant, Hilda and the Black Hound, Hilda and the Bird Parade, Hilda on the Stone Forest | Luke Pearson
  
• Julia's House for Lost Creatures, Little Robot, Nobody Likes a Goblin | Ben Hatke
  
• Kiki's Delivery Service, My Neighbor Totoro, Ponyo, The Secret World of Arrietty | Yonebayashi & Miyazaki
  
• Mighty Jack, Mighty Jack and the Goblin King | Ben Hatke
  
• Nightlights | Lorena Alvarez
  
• Nursery Rhyme Comics | Thompson, Mignola, Telgemeier, et al.
  
• Tamsin and the Deep | Brown & Cameron
  
• TOON books: The Shark King | R. Kikuo Johnson
  
• Usagi Yojimbo | Stan Sakai
  
• Zita the Spacegirl, Legends of Zita the Spacegirl, The Return of Zita the Spacegirl | Ben Hatke
  
  Ages 8+
  
  
  
• Adventure Time | Ryan North
  
• The Adventures of Tintin | Herge
  
• Amulet | Kazu Kibuishi
  
• Asterix | Goscinny & Uderzo
  
• Atomic Robo | Brian Clevinger
  
• The Backstagers | James Tynion IV
  
• Bone | Jeff Smith
  
• Five Worlds | Siegel & Siegel
  
• Howl's Moving Castle, Spirited Away | Hayao Miyazaki
  
• Moomin | Tove Jansson
  
• Mouse Guard: Fall 1152, Mouse Guard: Winter 1152, Mouse Guard: Legends of the Guard | David Petersen
  
• The Nameless City, The Stone Heart | Faith Erin Hicks
  
• Nimona | Noelle Stevenson
  
• Roller Girl | Victoria Jamieson
  
• Smile, Drama, Sisters, Ghosts | Raina Telgemeier
  
• Star Wars | Jason Aaron
  
• A Wrinkle in Time | Madeleine L'Engle
  
  Ages 12+
  
  
• Delilah Dirk and the Turkish Lieutenant, Delilah Dirk and the King's Shilling | Tony Cliff
  
• Giant Days | Allison & Cogar
  
• Nimona | Noelle Stevenson
  
  Resources:
  
  
• goodokbad
  
• comicbookresources
  
• comicsintheclassroom
  
• ilovelibraries
  
• pastemagazine
  
  EDIT: removed more superhero titles

Here's a few:

Amulet by Kazu Kibiushi - Great YA fantasy series perfect for his age, is a great adventure with shades of Ghibli, featuring airships, creatures and sword fights.

The Nameless City/The Stone Heart by Faith Erin Hicks - Another great fantasy/historical fiction series with street rats and political intrigue, with shades of manga and Avatar: The Last Airbender. Faith Erin Hicks is such a great artist/graphic novelist, you should check out her other stuff as well!

Speaking of that Avatar: The Last Airbender has some great comics that continue the story after the tv series ends. If your nephew hasn't seen the show, sit his butt down right now and make him watch it. One of the best television series (animated or otherwise) ever made.

Some others that I haven't read yet but hear rave reviews about is the Delilah Dirk series. If he liked Brody's Ghost, he'll probably like actual manga, so Naruto, Full Metal Alchemist or 20th Century Boys.

I love the Scott Pilgrim series, but I don't know if the sense of humor and lifestyle it explores would pique the interest of a 13 year old? More like older high school or college. That being said he might love it so what do I know.