Sued for WHAT? What is actionable here?
This is STUPID.
Defamation of character?
An obvious attempt to stir up crazy BLM terrorists to murder Rittenhouse? Etc etc
Depends how the language around the obvious factual error was worded. If the book states or implies that Rittenhouse was acting on some animus against black folks, or part of a group that that is thought to be associated with such animus, the publisher is in for a pocket-cleaning. That would be libel and defamation.
The correct information is available on the public record from sworn testimony. No wiggle room there.