What if my similar books are all Mangas? Should I mention them anyway? Will the agent/editor reading the query yuck upon that with “so this writer actually reads more Japanese comics than English novels??”
You’re pitching a novel, so those Mangas are a nonissue. They sell into a different market, to a different readership; they’re irrelevant to your novel’s reception or performance in its own market. If you feel compelled to show that you’ve done your research, you could include a line like, “The only books with a similar concept are Mangas,” but I think that muddies the query letter with unnecessary information. Focus on the fact that your project is fresh in your market, because that’s nothing to yuck upon.