Another romance novel that lived up to the hype! I thought Hoang's debut, The Kiss Quotient, was excellent and missed her second novel, but couldn't resist grabbing The Heart Principle from the lucky day shelf at the library. And, as I had read about in the million glowing reviews, Anna goes on a journey to hell and back, and the narrative is quite dark. It made me rife with anxiety for her and I wanted to scream at multiple characters and multiple occasions. And major forewarning about the realities of grief and family strife during hospice. But, damn, I applaud Hoang for tackling really difficult stuff that is close to her personally as a person on the autism spectrum and who has dealt with taking care of a loved one who is dying. It is still a great romance, quite steamy/open door in parts, with the absolutely requisite happy ending!