Towards Understanding Ahadith
A compilation of 3 books on the principles of Hadith, rendered into English.
Khayr al-Usul by Moulana Khair Muhamad Jalandhari
Definition of Hadith by Shah Abdul Haq Dehlwi
Nukhbatul Fikar by Imam Ibn Hajar Asqalani, with its commentary, Tuhfatud Durar by Mufti Saeed Palanpuri