It is a valuable work, whose author has limited it to the expected Imam al-Mahdi (may Allah hasten his coming.) The author begins the book with some prophetic traditions confirming the imamate of al-Mahdi (s). Then he mentions the traditions showing that Allah doesn?t leave the world without a ?Hujjah?. After that he mentions traditions talking about the disappearance of Imam al-Mahdi, his aspects, biography, rule, charismata and virtues and he mentions the signs that precede the appearance of Imam al-Mahdi (s) besides other subjects concerning him. Sheikh al-Mufeed, after mentioning the traditions that confirm the imamate of al-Mahdi, says: ?The traditions on that are numerous. The scholars of Hadith have written them down and classified them in their books. Among those, who have mentioned them with full details and explanation, is Abu Abdullah Muhammad bin Ibraheem an-Nu?mani in his book al-Ghayba?? The author has finished the book in Thil-Hijja 342AH. Sheikh Agha Buzurg at-Tehrani in his book ?athTharee?a? says: ?It appears, according to some references, that the book was called or known as Mala? al-Ayba fee Tool al-Ghayba.?