Allah, the Exalted, has brought the creation into existence for the purpose of worshipping Him. Proper worship depends mainly on the soundness of the Aqeedah of Tawheed, or the belief in the Oneness of Allah.
Understanding the concept of Tawheed (Monotheism), on the other hand, helps the Muslim know his Rabb better, this knowledge makes him more conscious and fearful of Allah, and more hopeful of His Mercy.
This book defines the concept of Tawheed, and exposes dubious beliefs and improper rituals that are conducive to Shirk, the gravest of all sins which condemns man to eternal torment in Hell.
It also discusses the status of the Prophet (S) and the incumbency of loving and reverting him.
In brief, this book is a must for every Muslim