The phrase "to require another volume" means that there is so much information or content that it cannot fit into one book, so a second book is needed. Full definition
Keeping these media platforms active requires a volume of high - quality content. (entrepreneur.com)
Like language and mental time travel, though, these huge subjects require a volume each rather than a mere chapter. (newscientist.com)
Some only exist in the Enterprise and Education editions of Windows, which require a volume - licensing agreement or monthly subscription fee. (howtogeek.com)