Post-Valentine’s Day may be the perfect time to consider the nature of lasting love. Many say it is the love that is friendship. Kentucky-born author Martin has crafted a debut novel in which lust plays a role, and also the hard-won satisfactions of modern family life. But it is friendship throughout adulthood that gives “The Queen of Hearts” the thought-provoking moments that complement its success as a page-turner. Two medical professionals — women who have stood together throughout their careers — find the nature of their relationship challenged by what may not have been settled and left behind in the past. Not the most original plot—but when told through the friends’ differing points of view, the tale opens up to allow for considerable depth.