This is a translation of the book Kitab Sharh 'Aja'ib al-Qalb (On the Elucidation of the Marvels of the Heart). The original Arabic volume is Book XXI (21) of the classic work Ihya 'Ulum al-Din (the Revival of the Religious Sciences), which was written by Imam Abu Hamid Al-Ghazzali.
To appreciate the value of this book, there are no better words than Imam an-Nawawi who said that if all the books of Islam disappeared except The Book of Allah and the Ihya, it would suffice you.
This volume elucidates the marvels of the heart. The Imam deals authoritatively with the heart's diseases and their cures.