Tangled Hearts introduces the Salina, Kansas, Ward. Hidden in the Heart mentions a couple of the characters from Tangled Hearts and also has ties to the Salina Ward. However, it's a stand-alone book and can be enjoyed without having read Tangled Hearts. Change of Heart is the love story of Christina, the four-year-old daughter of Cathee from Hidden in the Heart. Although I use the same characters, you will also be able to read Change of Heart without having read the other two books.