Use canned air to blow dust from the page edges. Be careful not to hold the can too close to the book as it may grind the dust in.
Dust the book and the page edges lightly with a feather duster. Do not use any spray-on dusting products.
Put a few drops of lighter fluid on a clean, soft cloth and gently wipe dirt and dust from the boards, or hardback covers. Repeat as needed and wipe away all remnants of lighter fluid when you're finished.
Take a glossy dust jacket off the book and gently wipe with a clean, slightly damp cloth. Don't saturate the dust jacket and dry it thoroughly.
Use a soft, clean cloth or a feather duster on a non-glossy dust jacket. Do not use any liquids as they may stain the jacket permanently. Some soil can be removed using a book eraser, available from library stores.
Buy a commercial product like Clean Cover Gel from a library store and follow the manufacturer's instructions. Do not apply too much product to the book as it may damage it. Some of the products produce toxic fumes, so use them sparingly in a well-ventilated space.