Liane Moriarty is an Australian author, so it's no wonder she became known in New Zealand only once Hollywood expressed an interest in one of her books (Big Little Lies). Some of her books are classified as "light and funny", others as "issues books".
The Husband's Secret is definitely an issues book, sad at times, though it's by no means heavy or depressing. It makes you think. It makes you wonder what you'd do if you were one of the characters. It makes you want to join a book club just to discuss it, and it makes you Google the book to see whether other readers have figured out the symbolism.
Oh, and I did like how the book was not actually about guessing the secret: it was revealed pretty early on.