An excellent book for non-Muslims explaining various aspects of Islam.
Author: Pete Seda
Publisher: Islamic Propagation Office in Rabwah
Source: http://www.islamhouse.com/p/1301
Concept of God in Major Religions.
Author: Zakir Naik
The Nine Conditions of the Testimony of Faith.
Author: Jamaal Zarabozo
Publisher: Al-Basheer Magazine
Source: http://www.islamhouse.com/p/1371
Undoubtedly, the heart leans towards those who are kind and gentle. It was said a long time ago: "Make your face happy and your words gentle, and you will be more beloved to the people than those who give them a gift". The one calling to the religion of Islam and dealing with other people has the utmost need to gather the people around him, and cause their hearts to lean towards him so that they will listen to him. Adorning himself with kindness and gentleness helps to achieve that goal with the grace of Allah.
A comprehensive explanation and commentary of the first 24 hadith of Imam al-Nawawi's classic compilation, Riyadh al-Saliheen.
Author: Abu Zakaria Al-Nawawi
Ibn Rajab al-Hanbali This is a treatise we have written concerning humility (Khushu') and the hearts meekness and breaking (inkisar) before the Lord. The basic meaning of Khushu', is the softness of the heart, its being gentle, still, submissive, broken, and yearning. When the heart is humble, so too is the hearing, seeing, heard, and face; indeed all the limbs and their actions are humbled, even speech. The source of the Khushu, that takes place in the heart is the gnosis of Allah's greatness, magnificence, and perfection.
Author: Ibn Rajab Al-Hanbali