I'm afraid the question isn't very clear, eah. Are you able to say what type of resource this is? And in what way do the contents need to be 'kept safe'?
If it's a matter of copyright, then whoever writes/compiles the book (ie your friend) automatically has and retains copyright. That is unless the copyright to the information and illustration within belongs to someone else, in which case the respective owners' permission will be needed.
If the book is to include sensitive or confidential information, then your friend will need to consider whether its publication is restricted by law.
Assuming your friend has the legal right to publish this book, then what he or she does with any valuable information gained in the course of their research is really up to them. It depends on its value, I suppose. Backing up manuscripts on paper and in digital format and then lodging them in a safe deposit box would seem the best protection. If it's not quite so valuable, then paper and/or digital backups kept in the home will suffice. I know of one person who regularly sends backup disks to members of her family around the country, 'just in case my house burns down'.