Mussar Movement Writings
The historic Mussar movement was started by Rabbi Israel Salanter in the mid-1800s and continued strong into the 1900s. Not only did it bring personal renewal to many Jews - it birthed the Yeshiva movement and enabled traditional Judaism to survive the crises of the twentieth century and thrive on into the twenty-first. The following teachings come from several generations of Rabbi Israel Salanter's disciples and colleagues and are all, broadly speaking, writings from the historical Mussar movement (ספרי תנועת מוסר). This whole collection of 100+ Mussar books is also available as a PDF here.
Chofetz Chaim (חפץ חיים)
Chofetz Chaim (חפץ חיים) was written in 1873 by Rabbi Yisrael Meir Kagan (רבי ישראל מאיר כהן) (1838-1933, Wikipedia) about the discipline of only speaking well of others. The book became so popular that it became his nickname.
Get Chofetz Chaim, A Lesson a Day: The Concepts and Laws of Proper Speech Arranged for Daily Study edited by Rabbis Shimon Finkelman and Yitzchak Berkowitz and published by Artscroll in 1995. 456 pages. There's also this two-volume set from 1998 with the same content but more portable.
A more recent in-depth work is Artscroll's Sefer Chofetz Chaim: The Laws of Lashon Hara Translated and Elucidated Including Practical Illustrations, Notes, and Halachic Indexes, published in 2021. 448 pages. There's also the smaller Student Size.
If you're looking for something a little smaller there's Artscroll's 2001 Chofetz Chaim Daily Companion: The Concepts and Laws of Proper Speech Arranged for Daily Study based on the daily reading program arranged by Rabbi Yehudah Zev Segal and edited by Michoel Rothschild. 282 pages. See also the pocketsize paperback edition from the same year and the earlier 1999 hardcover.
If you're looking for something even lighter there's the 2014 paperback Sefer Chafetz Chaim with a translation from the legendary Rabbi Shraga Silverstein which you can also get in weightless digital Kindle format! 106 pages.
For the children and teens in your life there's the Junior Chafetz Chaim, an easy-to-understand English adaptation of Sefer Chafetz Chaim that features callout boxes such as "Zoom In," "Good Point," "Words of Wisdom," and "Amazing Fact" and also includes "Examples" section which brings each halachah to life in a contemporary, age-appropriate story. 304 pages. Published by Israel Bookshop Publications in 2020 and then in 2022 followed up with the more comprehensive Junior Shemiras Lashon, 456 pages.
If you like stories there's The Concise Chafetz Chaim: A Page a Day Expanded Edition which includes close to 200 stories illustrating the laws about being mindful of one's speech, written by Rabbi Asher Wasserman and published by Feldheim in 2022. 288 pages. There's also the original Concise Chafetz Chaim: A Page a Day from 2013 without the stories. 164 pages.
There's also the Sefer Chofetz Chaim: Arranged for Daily Study published by the Israel Book Shop in 2015 and the 2017 Pocketsize Edition. 304 pages.
And last and possibly best, 2006 Mazal Press came out with the two-volume Chafetz Chayim: Sefer Shemirat HaLashon (Book of Guarding the Tongue), translated by Yedidya Levy and distributed by Felheim Publishers Jerusalem. In 2008 they came out with this four-volume set of Sefer Chafetz Chayim which covered not only the Halachot (laws) of Esurei Lashon Hara & Rechilut (forbidden negative speech and gossip) but also included the classic Makor Hachayim and Be’er Mayim Chayim Commentaries. These excellent works can be read online free along with the Chafetz Chaim's other works on the Mazal Press website.
The Measure of Man
To Turn The Many To Righteousness (מזכה את הרבים)
To Turn the Many to Righteousness or Mezake Harabim (מזכה את הרבים) is a chapter from Madregat Ha'Adam (מדרגת האדם) which was written at the height of the Mussar movement by Yosef Yozel Horwitz (יוסף יוזל הורוביץ) (1847-1919, Wikipedia), the famous Alter or Elder of Novardok.
Get the only English translation by Shraga Silverstein, published by Feldheim in 1987. 103 pages.
Pathways of Mussar
Pathways of Mussar is a translation of Nesivos HaMussar by Rav Avrohom Shmuel Finkel (1879-1951), the son of the great Alter of Slabodka Rabbi Nosson Tzvi Finkel (נתן צבי פינקל) (1849-1927, Wikipedia). Published by Feldheim in 2016, 256 pages. Get it here.
Heart of Elijah (לב אליהו)
Mussar Meditations
Sichos Mussar or Mussar Meditations are a collection of talks by Rav Yechezkel Levinstein (1885-1974, Wikipedia) about the Yomim Noraim or High Holydays and Elul, the Jewish month leading up to it. 85 pages. If not on Amazon try this search. It appears the next book contains this content also.
Legacy of the Mashgiach
Legacy of the Mashiach is a collection of the teachings of Rabbi Yechezkel Levenstein, the Mashgiach Ruchani or Spiritual Guide of the great Mir Yeshiva from Belarus, through Japan and China, and finally to Jerusalem. Published by Artscroll in 2009. Get it here.
Reb Chaim's Discourses
Sichos Mussar: Reb Chaim's Discourses is a collection of the shmuessen or Mussar talks of Rabbi Chaim Shmulevitz (חיים לייב שמואלביץ) (1902-1979, Wikipedia), Rosh Yeshiva to the great Mir Yeshiva from Poland through China to Jerusalem. Published by Artscroll in 1989. 272 pages. Get it here.
Alei Shur (עלי שור)
Rabbi Shlomo Wolbe (1914-2005, Wikipedia) was one of the greatest Ba'alei Mussar or Mussar masters of his generation and wrote Alei Shur (עלי שור/On the Wall), one of the best Mussar books to never be translated. The good news is that Rabbis Yoram Bogacz and Eliyahu Reingold did a set of English audio lectures on the two volumes of Alei Shur which you can listen to here.
Rav Wolbe on Chumash
Even though Rabbi Shlomo Wolbe's greatest work has never been translated into English (see above), at least some of his teachings are translated and organized according to the weekly Torah readings in Rav Wolbe on Chumash. Get Volume 1 (432 pages) and Volume 2 (456 pages), published by Artscroll in 2014 and 2016.
Majesty of Man
Majesty of Man: Torah Insights Into Human Nature were taken from the talks of Rabbi Henach Leibowitz (1918-2008, Wikipedia) and published by Artscroll as part of their Judaica Classics series in 1992. 284 pages. Get it here.
Mind Over Man: The Climb To Greatness
Mind Over Man: The Climb To Greatness. Rav Yechiel Yitzchok Perr (born 1935, Wikipedia) is a living link to the pre-war Mussar movement - grandson of Avraham Yoffen (1887-1970, Wikipedia), son-in-law of the legendary Yehuda Leib Nekritz (1907-1984, Wikipedia), and disciple of Aharon Kotler (1891-1962, Wikipedia). This book is a collection of his talks on the untranslated Madregat Ha'Adam by the Alter of Novardok, transcribed by Rabbi Yehuda Keilson and published 2017. 352 pages. Get it here.
Faith Over Fear: Path To Bitachon
Faith Over Fear: A Path To Bitachon. See previous book for information on Rabbi Yechiel Yitzchak Perr, a living link to the original Mussar movement. This book is a second collection of his talks on Madregat Ha'Adam, transcribed by Rabbi Yehuda Keilson and published 2019. 366 pages. Get it here.
Choosing Not To Choose
Choosing Not To Choose is based on the talks of Harav Yechiel Yitzchok Perr on Tekufos Ha'Ola, the first section of the classic Mussar work Madreigas Ha'Adam. Written by David Jemal and published by Tzidkus Press in 2022. 264 pages. Get it here.