The Heart Principle by Helen Hoang

The Heart Principle (The Kiss Quotient, #3)

by Helen Hoang

To most, Quan is a surly, underachieving playboy. Anna dislikes him, or so she tells herself. She will never admit that she harbours a secret crush on Quan, especially because he only has eyes for her charismatic younger sister Camilla. Now, with her sister's engagement on the line, Anna must bury her anxieties and overcome her OCD to try and seduce Quan and save her sister's impending marriage.

But when Quan discovers Anna's true intentions, he's forced to confront his own hurtful past and learn to forgive, while Anna must face her greatest challenge: truly opening herself up to love.

Reviewed by FranJessca @ A Book Lovin' Mama's Blog on

4 of 5 stars

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I fell in love with Helen Hoang’s ‘The Kiss Quotient’ when I read it back in 2019. I loved Stella and Michael’s story. I was excited to read Quan’s book, finally. In The Heart Principle, I was not prepared for an emotional roller coaster. 

Storyline/My Thoughts: This book put me through the wringer. I felt sympathetic for both main protagonists in the story, Anna Sun and Quan Diep, for very different reasons. 

Anna Sun achieved success when her playing the violin went viral. Now, she’s struggling with finding that success again. Now, on top of not having the ability to play her violin, she has her so-called jerk of a boyfriend that wants an open relationship. They’ve been together for a while now. He wants to make sure Anna is the one before he considers marrying her. (Believe me when I say her jerk of a boyfriend didn’t win me over at all in this book.) Anna hasn’t been with anyone else but her boyfriend but decides to try a one-night stand. Unfortunately, Anna isn’t sure she can even commit to those successfully.

Anna meets Quan Diep online, and he’s not looking for a serious relationship. They both agree to a one-night stand, but unfortunately, it doesn’t work out to be a successful one-night stand since Anna has never had one before.

Quan has had a hard life, too. He has gone through something in his life that changed him. He never thought he could have a happily ever after until he started to know Anna. The minute Anna and Quan start getting closer together, tragedy strikes in Anna’s life, and she has to help her family with her father. This is when the story focuses more on Anna and what she is going through with her family of becoming her father’s caregiver.

The minute the story shifts focus to what Anna is dealing with when it comes to caring for her father with her mother and sister, the story becomes emotional to me. I was not too fond of Anna’s sister in the story. She drove me crazy with how she treated Anna. One of the parts I knew I was not going to like Anna’s sister is when Anna tries to confide in her sister about what she finds out about herself. Her sister, instead, doesn’t believe Anna. Grrrr! Don’t even get me started on how they have constantly belittled Anna throughout her life. They expect so much out of Anna without considering what she needs in her life. There were times I wanted to go through the book and help Anna with her family and how they treated her.

This book doesn’t focus much on romance, but it does have it. It focuses more on mental health and caregiving burnout. There’s also where Anna finds out she has Autism Spectrum Disorder, which Helen Hoang is the only author I’ve read so far that has characters with autism in her books.

There is romance in the book, but this romance has a lot of drama. Anna is dealing with so much that she is still confused with her relationship with her boyfriend. She is mistaken for her feelings with Quan and doesn’t know how to communicate her feelings to him. There’s a moment that Anna broke me on how she handled being with Quan. I won’t ruin it for readers who haven’t read this book yet.

I’m glad this book does have a happily ever after; the characters go through so much to get there. I was rooting for Anna to have a happily ever after because she deserved it after everything she has gone through in life with her family. Quan also deserved a happily ever after, especially finding out what happened to him.

Overall, this story gets four stars from me. Yes, I wish there was more steam in this book, but I enjoyed getting to know Anna and Quan in their story.

Helen’s author note at the end broke me into pieces. Helen put a lot into this book that she was going through at the time in her life. She has become one of my auto-buy authors because the characters she writes in her stories are lovable and feel real to me. Helen’s characters are ones that I will never forget.

Standalone or Part of Series: It’s part of the Kiss Quotient series, but each can be read as a standalone.

Steaminess: ⭐️ ⭐️ ⭐️ 💫

Trope: Slow Burn; (Failed) One Night Stand

HEA: Yes.

Would I recommend this book? Yes. If you enjoy Contemporary Romance or Women’s Fiction novels, then you’ll enjoy this book/series by Helen Hoang.

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Reading updates

  • 14 December, 2021: Started reading
  • 14 December, 2021: on page 0 out of 304 0%
  • 18 December, 2021: Finished reading
  • 29 December, 2021: Reviewed