From the author's point of view, where I have been involved in licencing photos for my books there are questions you have to ask.
1. Who is requesting the licence? Is it the author or the publisher? These days publishers are increasingly trying to download clearances and licencing fees on authors. Some publishers don't tell the author the print run or low ball it. Print runs are often considered proprietary information and not always given up front. Insist on dealing directly with the publisher, not the author, to make sure that everything is clear to you.
2. Make sure you have a signed contract with the publisher that spells out the rights licenced. In case of e-books check to see if the territorial limitations match the print run. These days while the print run may be US and Canada, the e-book may be licenced worldwide. (Amazon does have territorial restrictions on Kindle, but not all others do.) Also check to see if the contract allows use by other branches within the same corporation, that's a sneaky one that I am told Murdoch's News Corp which owns Harper Collins tries to use, but in case of authors represented by agents, that clause is struck or payment is part of it, usually 50% to the publisher and 50% to the author. So again the cover is fair dealing/fair use but what if a corporate publisher wants to use your image in a company owned magazine?
3. Subsidiary uses..... reproduction of the cover is fair use. What if the publisher wants to supply the original image to the media as part of a press package? That could mean, if you're not careful, the image could end up in everyone's archives with no restrictions. If the publisher wants your image as part of a press package sometimes you can negotiate a time limit on media use (but not everyone adheres to restrictions)
4.Getty is not always a good guide. Getty has contracts with big book publishers that are similar to the contracts the news media sign which provide discounts and multi use. For my last book, I needed a picture of the British surrender of Singapore. There are about a dozen available, but only one had the right angle that showed the main character in the book, and Getty had that one. My publisher was able to get the image much cheaper than the quoted price, because they had the Getty contract. (the publisher objected to the cost of a couple of other images but with Getty they said "no problem, we've got a contract.")
5 NO foreign language rights. Who sells the foreign language rights depends on the contract with the author. These days it is sometimes the publisher, but often the author's agent. The foreign publisher usually wants to design their own cover on the basis of the local market, but sometimes the cover art is sent and the translated title is put over the art. So the publisher might ship a package to the foreign rights holder and not bother to check with you.
Most of this won't matter because most books don't "earn out" that means repay their advances and the author goes into profit, but you never know. Another thing to know is that if the book does go into a second printing, make sure you, as the photographer, get the money up front. Author's are not always paid because books are a commodity business and publishers are entitled to hold a "reserve against returns." The one book I worked on, a computer manual, that did "earn out" payment didn't start coming in until two years later.
RR