If you're the only author of a book, your name will be the only one on the cover. But what if a book has more than one author, then what?
Names are important, and the sequence of names on a book's cover and subtitle page can make a difference. Sometimes the "lead author" is the person with a more recognizable name, so it makes good marketing sense to put that person's name first.
If recognition within the market isn't a factor, though, then generally the authors decide the sequence of names. Maybe they'll decide that the first name is the name of the person who wrote the most content.
Maybe it'll be the person who coordinated the entire project.
If the authors are all from the same school, maybe the lead author will be the one with the highest position in the organization.
Regardless of the sequence, the royalties may be split completely differently. That's right, who gets what percentage of the royalties has nothing whatsoever to do with the sequence of names on the cover.
In fact, sometimes the people listed on the cover don't receive royalties at all. Maybe they were paid on a work-for-hire arrangement, a one-time fee paid regardless of how well a book sells.
Basically, the sequence of names on a cover often mean more to the authors than to the publisher. So, what to do when the authors can't agree on a sequence?
We look for other alternatives. For instance, I had two authors who worked together for years on two different textbooks. They used one person's name first for one book and the other's name first for the other book.
I've had other author teams that list their names alphabetically.
I've known author teams who switch the lead author names each edition, though I don't advise it. After an edition or two, it becomes difficult for people to find the book.
If push comes to shove, the decision is made by the acquisitions editor because that's the person who has final responsibility for the book.
I don't particularly like doing that. I'd much rather have the authors reach consensus, but when they can't, well, gol-dang it, I pull the trigger.