What is the best methodology (books and audio lectures) for self-purification, spiritual edification, and mending hearts, and what is the importance of this branch of knowledge?

The science of rectifying hearts and clarifying the path to Allah Almighty is among the most noble of sciences. A servant is in greater need of it than food and drink, because with the rectification of the heart, the entire body becomes rectified, and Allah looks at the hearts of His servants. The way to learn it is by adhering to the Qur’an and Sunnah, and understanding the words of Allah and the words of His Prophet (peace be upon him). Scholars have dedicated entire works to these matters. Among the most important books are: "Ihya’ Ulum al-Din" by al-Ghazali (with its abridgements and refinements such as "Minhaj al-Qasidin" by Ibn al-Jawzi and "Maw’izhat al-Mu’minin" by al-Qasimi), and "Madarij al-Salikin" by Ibn al-Qayyim, which is a commentary on "Manazil al-Sa’irin" by al-Harawi. It is recommended to start with "Al-Tuhfa al-Iraqiyyah" by Shaykh al-Islam, then an abridgement of "Madarij al-Salikin," and a summary of "Minhaj al-Qasidin." Also, one should frequently read the works of Shaykh al-Islam Ibn Taymiyyah and his student Ibn al-Qayyim, and the words of Ibn Rajab. There are also many beneficial contemporary lectures and audio lessons available.