What's the best way to clean a book's hardbound cover?
Answers:
1 cup full of vinegar in a bucket of cool water, use dampened sponge & gently wipe, dust or blot or both, do not soak the cover! the key word here is "gently", wipe with paper towel, prefereably VIVA, as it is cloth like, or use soft rag.
Other answers:
What ever you do to these, it will be apparent unless you use a compressor.
Aim the compressor hose at the cover, holding it shut with one hand so the pages don't get damaged from the book blowing open. The air will dislodge any loose dirt but not damage the cloth. Never use a liquid, never use a cloth since the fibers of the cloth can become more of a problem as they adhere to the book cover.
Restoration artist.
What ever you do to these, it will be apparent unless you use a compressor.
Aim the compressor hose at the cover, holding it shut with one hand so the pages don't get damaged from the book blowing open. The air will dislodge any loose dirt but not damage the cloth. Never use a liquid, never use a cloth since the fibers of the cloth can become more of a problem as they adhere to the book cover.
Restoration artist.
I would use a very very fine (maybe 400 grit) sandpaper
Have you tried a MR Clean magic eraser? It's the first thing I'd try. Second choice, a dry sponge from a cleaning supply company--you can learn about them from the link below.
Definitely do not use liquid of any kind.