Ahadith began to be put down in writing even during the era of the Prophet (S), but these Ahadith were no better than compilations individuals. Their purpose was just to put them down in writing, with: regard for order or sequence. Later, during the caliphate of ‘Umar bin ‘Abdul-‘Aziz (99 AH-101 AH), the state undertook this task but most of the works in this field were the products of individual labor. During the second century of the Hijra calendar, famous books like Muwatta’ of Imam Malik and Musnad of Imam Shafi were prepared but the third stage recording Ahadith, known as the Golden Age, came only in the third century AH. Many collections were made in this age. These included the Six Books (Kutub Sittah), popularly known as the Sound Six (Sahah Sitta), Sunan of Ibn Majah being one of them and considered the last of them.
Sunan Ibn Majah began to be included in the Six Books by the end of the fifth century AH. Since then, in every succeeding age, it kept on growing value and importance. With respect to soundness and strength, Sunan Ad Darimi, Sunan Ad-Daraqutni and other books of Sunan were superior Sunan Ibn Majah but they did not gain popularity like Sunan Ibn Majah.
It is to be noted that Sunan is a technical term used by scholars of Had sciences to denote a book of Ahadith relating to legal rulings, from the Chapters of Purification down to the Chapter on Wills in the same order as followed in books of Islamic jurisprudence.
How important and useful the Sunan Ibn Majah is, can also be gauged the fact that when Ibn Majah showed his work to Imam Abu Zar’ah, the latter remarked: ‘If this book reached the public, all or most of the existing Jawami would cease to be used. The words of Imam Abu Zar’ah proved be true to the last letter. Several Jawami, Musnads and Sunan were eclipsed by Ibn Majah’s Sunan.
Hafiz Ibn Hajar termed the book Jami’ Jaiyid (a good, comprehensive Hadith collection).
The book, As-Sunan by Imam Ibn Majah was an excellent and beneficial work that stunned the scholars of his time.
He himself said about the book: “I showed this book to Abu Zur’ah Razi. He checked it and said, ‘I think if people lay their hands on this book, all or most of other great compiled works will become unnecessary.”
Source: PDFs and information taken from kalamUllah.com