What is vizbig?
VIZBIG is VIZ Media's oversized omnibus line. For Vagabond it is 12 books covering the 37 singles, three story volumes to a book.
The name is a brand, not a format by itself. A VIZBIG book is an omnibus edition with its own numbering, trim size, and usually its own ISBNs. Vagabond's VIZBIG edition is the clearest case in the catalog: 12 omnibuses against 37 singles, and the singles are a finished set because the series is on hiatus.
People say “I own Vagabond” and mean either set. The two do not add together. Twelve VIZBIG books can be a complete run of the singles. Twelve singles are the beginning of the single set. Hondana's Vagabond page lists both lines so the count has an edition attached.
Other publishers do the same thing under other names: Dark Horse Deluxe, VIZ's Perfect Edition, Kodansha's hardcover omnibuses. The catalog records the name the book actually uses.
Related
See the words on a real set in the edition catalog.