6 main books of hadith!
بسم الله الرحمن الرحيم
There were many who recorded Hadith (the term "Sunnah" also reffers to Hadith which is defined as the sayings and doings of Prophet Mohammed)..
Bukhari & Muslim were the most reliable 2, that scholars described thier books "Sahih Bukhari" & "Sahih Muslim" as the most righteous After the book of The Holy Quran.
Other than these two, All Scholars Agreed to rely on 4 Hadith recoders beside Bukhari and Muslim, to be 6 major books of Hadith:
1. Sahih Bukhari, collected by al-Bukhari (d. 870), included 7275 hadiths
2. Sahih Muslim, collected by Muslim b. al-Hajjaj (d. 875), included 9200
3. Sunan al-Sughra, collected by al-Nasa'i (d. 915)
4. Sunan Abi Da'ud, collected by Abu Da'ud (d. 888)
5. Sunan al-Tirmidhi, collected by al-Tirmidhi (d. 892)
6. Al-Muwatta, collected by Imam Malik (d. 796) and sometimes it is referred to Sunan Ibn Majah, collected by Ibn Majah (d. 886). Some people even consider Sunan al-Darami to be the sixth one.