His latest work is a monumental piece exceeding 1000 pages.
This epic film is a trilogy, totaling nine hours.
長編 simply means a long work, while 巨編 implies not just length but also monumental ambition or quality.
Standard kanji spelling for a massive literary or cinematic work.
Variant kanji spelling using 篇; less common but still seen.
Compound of 巨 (きょ, 'huge') and 編 (へん, 'compilation' or 'volume'), literally meaning a huge volume or compilation.