Non Monogamy Guidance

The Ethical Slut A Practical Guide to Polyamory, Open Relationships, and Other Freedoms in Sex and Love by Janet W. Hardy, Dossie Easton

Opening Up: A Guide To Creating and Sustaining Open Relationships by Tristan Taormino

Polysecure by Jessica Fern

Improving Intimacy

Deshamifying: The Power of Vulnerability by Brené Brown

Deshamifying Women’s Sexuality: Come as You Are by Emily Nagoski

Deshamifying Men’s Sexuality: Cockfidence: The Definitive Guide to Being the Man You Want to Be and Driving Women Wild by Danielle Harel Ph.D, Celeste Hirschman M.A

Understanding your Eroticism: The Erotic Mind: Unlocking the Inner Sources of Passion and Fulfillment by Jack Morin

Attachment: Wired for Love by Stan Tatkin (Chapters 2-4). Wikipedia Page on Attachment Theory is also quite good (stop after attachment in adults.)

Repair: Making Love Real: The Intelligent Couple's Guide to Lasting Intimacy and Passion by Danielle Harel Ph.D, Celeste Hirschman M.A

BDSM

Wild Side Sex: The Book of Kink by Midori

The Ultimate Guide to Kink by Tristan Taormino