To preserve the book, leaf through it and remove any bookmarks that may be there.

Dust off the pages if they need it, as well as the cover.

Store it in a room with as little temperature and humidity change as possible, either laid flat or upright between bookends or other books. You don't want it laying on a diagonal with empty space around it and supported only by the corners.

Keep it away from sunlight, as this is a sure way to begin deterioration or the pages.

Check it periodically for paper-boring pests.

If you notice any deterioration or pests, have it conserved. If no deterioration is present, conservation would cost more than the value you'd get from the process.