By John Dunning (Scribner: 2004)

Ex-cop and current rare book seeker Cliff Janeway buys a very valuable book at auction, paying over $29,000 for a signed copy of a first edition by the legendary nineteenth-century explorer Richard Francis Burton (not the actor). Soon afterward a very old and nearly blind

woman makes her way from Baltimore to his shop in Denver to tell him that the book really belongs to her. At first he doesn’t believe her, of course, but soon he sees that he will never rest until he’s sure of the truth of the matter. --That’s where the ‘promise’ in the title comes in.
The quest for Richard Burton’s books and experiences in 1860 leads Janeway to Charleston where he learns of Burton’s involvement in the beginning of the Civil War, something that historians had heard about but of which they had no proof.
Several people die in this book and there’s much suspense and danger. There’s also a woman Cliff finds “interesting,” but at the end of the book they are still only good friends.
All of Dunning’s books are excellent and just short of being of the ‘can’t-put-down’ level.