Mosaic is a novel written by Jeri Taylor that provides some back-story on characters from Star Trek: Voyager, including Kathryn Janeway. It possesses the dubious distinction of being the only novel to be accepted as part of Star Trek canon, and even then it didn't last.
- Canon is what's produced for the TV and Movie screens. Books aren't. End of story. It's my job to hold licensees like Pocket to that standard. Which is not to say that there haven't been times when canon has contradicted itself—those darn producers and scriptwriters don't always keep track of/remember/care about what's come before. So things can get confusing. But books are never considered part of canon. The only reason Jeri Taylor's books were considered quasi-canon for a while was because licensees really wanted some sort of background structure they could utilize for the Voyager characters (they find it hard to accept statements like "Well, they haven't established that on the show yet .."). So we (by this I mean VCP and folks in Rick Berman's office, whom I consulted with) let them consider Jeri's stuff quasi-canon. It didn't seem to hurt anything.
- --Paula Block, head of Star Trek licensing at Paramount
So, basically, Jeri Taylor's novel was temporarily kinda-sorta canon.