I would've loved to see Quan and Anna step outside their bubble and interact in more social settings together, but it feels just as good to see them learn about each other without external influences (although her family certainly tries) ... It's a little on the nose to say that Hoang's new romance is sex-positive, but it's important to show how she neutralizes the social pressures around physical intimacy ... Perhaps one of the hardest parts of reading this book is the visceral reaction to seeing other people mistreat Anna and Quan because of their differences. We want to protect them while we collectively bemoan their loss of agency. So much of the story manifests the act of grieving ... It's an emotional journey, but a fulfilling one to watch Anna and Quan not only reconcile with the limits of their bodies and health but wield enough power to stand up for themselves. In fact, it's evident that while Anna's autism is a turning point for her, it's not meant to define her or the story; if anything, it's just the missing puzzle piece that lets her fully love herself without a nagging sense of uncertainty ... Having read all three of Helen Hoang's books, I can confidently say she's a consummate wordsmith of soulful romances, with soft, honest-to-goodness love stories paired with euphoric steaminess. The Heart Principle wears its heart on its sleeve. While it's thematically heavier than her previous books, Hoang's writing breathes with the kind of kinetic power and acceptance that feel freeing because she lets her characters fully realize themselves — even when those around them can't.

... a gripping love story ... riveting the whole way through, exploring a complex range of subjects in unique and interesting ways. Anna and Quan are an exciting, dynamic pair, their chemistry palpable as they fall deeper and deeper in love.

Quan will instantly win over readers with his wonderful combination of bad boy vibes on the outside and an adorably gooey center on the inside ... Reading a Hoang romance often involves tears, given her knack for homing in on uncomfortable emotions and human vulnerability. The Heart Principle is no different, and it will offer much-needed catharsis to readers who can identify with Anna’s burnout and restlessness ... Those who have been fans of Hoang’s contemporary romances since the beginning will be overjoyed to finally get Quan’s story. It does not disappoint. And new readers will most likely sprint to the nearest library or bookstore to get their hands on Hoang’s other two books. That’s how much The Heart Principle lives up to the hype: Hoang has once again displayed her mastery of both complicated emotions and naturalistic, earthy eroticism.

Hoang’s latest delivers everything her fans have come to expect: thoughtful explorations of neurodiversity, steamy love scenes, and relatable characters. The first-person narration adds a feeling of intimacy and immediacy to the story. Readers will be delighted that Quan has met his match; this is also a good pick for fans of Talia Hibbert.

Readers of Hoang’s other Kiss Quotient books may be surprised by this third installment’s heavy plot points, which weigh down the narrative. Hoang writes a sparkling romance between Quan and Anna, but this novel is very much about Anna’s finding her voice and setting boundaries.

... beautifully melancholy and meditative ... Hoang strikes a more somber tone in this outing, giving Anna daunting challenges to overcome, including some serious hang-ups around sex. Readers shouldn’t expect a typical rom-com, but many will still swoon for this sensitive love story.

Hoang unflinchingly describes the physically exhausting work of caretaking, which is coupled with Anna’s emotionally wrenching conviction that her father does not want to live this way. The primary themes in the second half are about filial piety and how Anna’s endless self-sacrifice without corresponding acceptance from her family pushes her to create limits and boundaries. Quan is a solid, steady presence but mostly relegated to the back burner. In the afterword, Hoang calls the book 'half memoir,' which helps explain why it feels like half a romance. Genre readers will have to judge for themselves if the romance plot satisfies, but those desperate for fiction that explores the crushing weight of caregiving will find it here ... Grief and suffering make for an emotionally moving novel, but without fully exploring healing and recovery, is it a romance?