Alright, so this is a bit of a tricky one because "the goddess book" is honestly a pretty vague term. If you're talking about that ultra-popular urban fantasy series that starts with 'Moon Called' by Patricia Briggs, the central character is Mercy Thompson, who's a Volkswagen mechanic and a walker (shapeshifter into a coyote), not a goddess at all. But if you mean a book literally titled something like 'The Goddess Book' or 'Goddess', things get fuzzy.
My first instinct went to a novel I read years ago called 'The Goddess Chronicle' by Natsuo Kirino, which is a retelling of the Japanese myth of Izanami and Izanagi—so the central figures are those gods. But that might not be it either. Sometimes people use "the goddess book" as shorthand for 'Circe' by Madeline Miller, where the central character is obviously the witch-goddess Circe from Greek myth. That book's had a massive surge in popularity lately, so odds are decent that's what someone's asking about.