Sexual ethics

Free to read here, from Project Gutenberg.

Plain Facts for Old and Young

John Harvey Kellogg

The Task of Social Hygiene

Havelock Ellis

Sex & Character

Otto Weininger

The Ladies Book of Useful Information

Anonymous

The Sexual Life of Our Time in Its Relations to Modern Civilization

Iwan Bloch

Sexual Life of Primitive People

Hans Fehlinger

Confessions of Zeno

Italo Svevo

Searchlights on Health: Light on Dark Corners

B. G. Jefferis and J. L. Nichols

Searchlights on Health: The Science of Eugenics

B. G. Jefferis and J. L. Nichols

Geschlecht und Charakter: Eine prinzipielle Untersuchung

Otto Weininger

German

Sane Sex Life and Sane Sex Living

H. W. Long

Little Essays of Love and Virtue

Havelock Ellis

The Delights of Wisdom Pertaining to Conjugial Love

Emanuel Swedenborg

Youth and Sex: Dangers and Safeguards for Girls and Boys

Mary Scharlieb and Frederick Arthur Sibly

The Biology, Physiology and Sociology of Reproduction

Winfield Scott Hall

What a Young Woman Ought to Know

Mary Wood-Allen

Sexual ethics

Auguste Forel

Sex-Love, and Its Place in a Free Society

Edward Carpenter

Women As Sex Vendors

R. B. Tobias and Mary Marcy

What a Young Husband Ought to Know

Sylvanus Stall

Plain Talks on Avoided Subjects

Henry N. Guernsey

Supplément au Voyage de Bougainville

Denis Diderot

French

Love—Marriage—Birth Control

Bertrand Edward Dawson Dawson, Viscount

Hands Around [Reigen]: A Cycle of Ten Dialogues

Arthur Schnitzler

Almost a Woman

Mary Wood-Allen

The Power of Womanhood, or Mothers and Sons

Ellice Hopkins

An Outline of Sexual Morality

Kenneth Ingram

Venere ed Imene al tribunale della penitenza: manuale dei confessori

J. B. Bouvier

Italian

Some Phases of Sexual Morality and Church Discipline in Colonial New England

Charles Francis Adams

Herself: Talks with Women Concerning Themselves

E. B. Lowry

Child Life and Sex Hygiene: A Remarkable Message

Otterbein Oscar Smith

Essays in medical sociology, Volume 1 (of 2)

Elizabeth Blackwell

Almost A Man

Mary Wood-Allen

Love's Coming-of-Age: A series of papers on the relations of the sexes

Edward Carpenter, also an audiobook

Sex and Common-Sense

A. Maude Royden

The unwelcome child

Henry Clarke Wright

The whore

Whore of Quality

Why not? A book for every woman

Horatio Robinson Storer

Al mia fratineto: Letero pri la seksvivo

Felix Ortt

Esperanto

Essays in medical sociology, Volume 2 (of 2)

Elizabeth Blackwell

Is it I? A book for every man.

Horatio Robinson Storer

A Treatise on the Crime of Onan

S. A. D. Tissot

Le parfum de la Dame Noire

Louis Sonolet and Paul Bourgette

French

Men, Women, and God

A. Herbert Gray

The hour before the dawn

Josephine Elizabeth Grey Butler