10 of the Most Popular Mussar Books:

Duties of the Heart (חובות הלבבות)

Laws of Personality (הלכות דעות)

Gates of Repentance (שערי תשובה)

Ways of the Righteous (אורחות צדיקים)

Path of the Just (מסילת ישרים)

Accounting of the Soul (חשבון הנפש)

Light of Israel (אור ישראל)

Strive For Truth! (מכתב מאליהו)

Everyday Holiness

With Heart In Mind

Full List of Mussar Books Here:

https://ia902207.us.archive.org/32/items/mussar-books/List%20of%20100%2B%20Mussar%20Books%20-%20Best%2C%20Rabbinic%2C%20Classic%2C%20Historic%20Movement%2C%20Modern%20%28Mussar%20Center%20%40%20mussar.org%29.pdf