I recently came across this list of books on poly/cnm/open relationships.
I've read 15 or so of them. I found both the histories interesting, and since they each had a different emphasis, it was worth reading both of them.
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American Poly: A History
Christopher M Gleason
The Anxious Person’s Guide to Non-Monogamy
Lola Phoenix
The Art and Etiquette of Polyamory
Francoise Simpere
The Art of Relationship Anarchy: A Revolutionary Approach to Love, Intimacy, and Connection - Deanne Meyers
Ask Me About Polyamory – Kimichi Kuddles
Tikva Wolf
Beyond Monogamy, Polyamory and the Future of Polyqueer Sexualities
Mimi Schippers
Designer Relationships: A Guide to Happy Monogamy, Positive Polyamory, and Optimistic Open Relationships
Mark Michaels and Patricia Johnson
Eight Things I Wish I'd Known About Polyamory: Before I Tried It and Frakked It Up
Cunning Minx
The Ethical Slut, Third Edition: A Practical Guide to Polyamory, Open Relationships, and Other Freedoms in Sex and Love
Janet Hardy and Dossie Eason
Fifty Years of Polyamory in America
Glen W Olson, Terry Lee Brussel-Rogers
Fraught Intimacies: Non-Monogamy in the Public Sphere
Nathan Rambukkana
A Happy Life in an Open Relationship
Susan Wenzel
Hot to the Touch: Views from the Polyamory Lifestyle
Cole Riley
It's Called "Polyamory": Coming Out About Your Nonmonogamous Relationships
Tamara Pinctus and Rebecca Hiles
The Jealousy Workbook
Kathy Labriola
Kaleidoscope of Polyamory: How Ready are You for an Open Relationship?
Mint Rabbit
The Lesbian Polyamory Reader
Marcia Munson, Judith Stelboum
Let’s Talk About …Non-Monogamy
JR James
The Many Faces of Polyamory: Longing and Belonging in Consensual Relationships
Magdalena J Fosse
Many Loves: A Memoir of Polyamory and Finding Love(s)
Sophie Lucido Johnson
More: A Memoir of an Open Marriage
Molly Roden Winter
More Than Two: A Practical Guide to Ethical Polyamory
Franklin Veaux, Eve Rickert
Multiamory: Essential Tools for Modern Relationships
Winston, Lingren, and Matlack
The Myth of Monogamy: Fidelity and Infidelity in Animals and People
Judith Eve Lipton, David P. Barash
The New Love Without Limits
Deborah Anapol
Open: An Uncensored Memoir of Love, Liberation, and Non-Monogamy
Rachel Krantz
Open Monogamy: A Guide to Co-Creating Your Ideal Relationship Agreement
Tammy Nelson
Opening Up: A Guide to Creating and Sustaining Open Relationships
Tristan Taomino
Poly Land: My Brutally Honest Adventures in Polyamory
Page Turner
The Polyamorists Next Door
Elisabeth Shef
Polyamory: A Clinical Toolkit for Therapists (and Their Clients)
Martha Kauppi
Polyamory and Jealousy
Franklin Veaux, Eve Rickert
Polyamory and Kink
Jess Mahler
The Polyamory Breakup Book
Kathy Labriola
Polyamory in the 21st Century
Deborah Anapol
Polysecure: Attachment Trauma and Consensual Non-Monogamy
Jessica Fern
Polywise: A Deeper Dive into Navigating Open Relationships
Jessica Fern and David Cooley
Power Circuits: Polyamory in a Power Dynamic
Raven Kaldera
Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships
Christopher Ryan and Cacilda Jetha
Relationship Anarchy: Occupy Intimacy!
Juan-Carlos Pérez-Cortés
Stepping Off the Relationship Escalator: Uncommon Love and Life
Amy Gahran
Stories from the Polycule: Real Life in Polyamorous Families
Elizabeth Shef
The Smart Girl’s Guide to Polyamory
Dedeker Winston
A Therapist’s Guide to Consensual Non-Monogamy, Polyamory, Swinging, and Open Marriage
Rhea Orion
Thriving in Non Monogamy An Ethical Slut's Guide: Overcome Jealousy, Enjoy Sex, and Honor Yourself
Erin Davidson
Understanding Non-Monogamies
Meg Barker and Darren Landridge
Understanding Threesomes Gender, Sex, and Consensual Non-Monogamy
Ryan Scoats
Undoing Monogamy: The Politics of Science and the Possibilities of Biology
Angela Willey
Why It’s OK to Not Be Monogamous
Justin L. Clardy
Wide Open: My Adventures in Polyamory, Open Marriage, and Loving on My Own Terms
Gracie X