Start with high-confidence love & romance books, then narrow by subgenre or adjacent topics.
The Grief Recovery Handbook, 20th Anniversary Expanded Edition
John W. James, Russell Friedman
The State of Affairs
Esther Perel, Harper
The Grieving Brain
Mary-Frances O'Connor, Mary-Frances O'Connor
The Love Prescription
John Gottman PhD, Julie Schwartz Gottman PhD
How Not to Hate Your Husband After Kids
Jancee Dunn
The Ethical Slut, Third Edition
Janet W. Hardy, Dossie Easton
Conversations on Love
Natasha Lunn
How to Love Better
Yung Pueblo
A Marriage at Sea
Sophie Elmhirst
His Needs, Her Needs
Willard F. Harley Jr.
Love Worth Making
Stephen Snyder M.D., Stephen Snyder
A Year and Six Seconds
Isabel Gillies
Eight Dates
John Gottman Ph.D., Julie Schwartz Gottman PhD
Attached
Amir Levine, Rachel Heller
Questions for Couples Journal
Maggie Reyes
The Couple's Activity Book
Crystal Schwanke
Sex Talks
Vanessa Marin, Xander Marin