From an attorney…
If two authors work together to write a book, they become joint owners
in the copyright to the book. Unless the writing was separated in some
easily discernable way, both authors own 50% of the work and each have
all of the rights that a single author would have. If both authors
contributed to every chapter and worked together to decide on wording,
there is no way to differentiate between their work and therefore no
method to divide the copyright.
On the other hand, if each author wrote certain chapters of the book and
those chapters could be separated without destroying the work, then
there might be a way to divide the copyright. Typically, that is not the
case. The applicable federal law states that “a ‘joint work’ is a work
prepared by two or more authors with the intention that their
contributions be merged into inseparable or interdependent parts of a
unitary whole.”
Co-authorship can be problematic because both creators have the right to
commercialize and monetize the product and can easily (and frequently
do) interfere with each other’s efforts if there is a lack of
cooperation.
When co-authorship is contemplated, it is recommended that they enter
into a written assignment of the copyright to avoid joint ownership of
the copyright. One of the authors can assign his rights to the other
author in exchange for compensation, recognition, and other negotiated
terms.
If the co-authors cannot agree on one owner, they can both assign the
copyright to a company in which they both have an ownership interest.
The company, such as a limited liability company, should be governed by a
written agreement between the owners. That agreement should include the
rights and obligations of the respective members, how to deal with
contingencies such as the death of one of the owners, buyout provisions
by one owner of the other’s interest, as well as other operational
matters.
When a creative work is owned by only one person or one entity, there is
a clearer direction for commercialization of the work and there are far
fewer disputes over the respective rights and obligations of the
parties.