Facts about the company's history are not protected under copyright. FYI, though you probably already know it, you also can't disclose company trade secrets -- so no posting the secret bagel recipe. Also, you probably want to avoid any trademark related claims by indicating that the book is not an "authorized" history.
What about the products and ads? If any of the ads were published before 1923, they are not protected under copyright. (This chart will help you sort out which ads are in the public domain.) Even if copyright exists, chances are good that your reproduction will constitute a fair use as you are using the ads for purposes of commentary. You're probably fine with product imagery, too, as your reproduction would also likely be considered a fair use. Legally, the photographer (or whoever the photographer transferred the rights to) would own the copyright but typically, slavish reproduction of products will trigger limited copyright protection (despite what some companies may argue). Also, that's a general rule and ultimately depends on the creative details of the packaging, and the attitude of the copyright owner. In addition, check out Section 113(c) of the Copyright Act which is not exactly on point, but by analogy seems to permit informational uses of product imagery. Although we don't want to influence your writing, the fact that your history is "favorable" may quell any gathering copyright storms.
PS, no, the book cover isn't real, although you can feel free to use it if you're writing a fictional history of a bagel business. (We did work briefly in a bagel bakery and even burned our fingers grabbing and dropping hot onion bialys -- and the boss said, "What? Too heavy for you?" ).