Early Christianity: An introduction to current scholarship on the origins of Christian theology within the first five centuries following the completion of the New Testament
The Origins of Early Christian Literature, by Robyn Faith Walsh
Brian Daley, SJ (Wikipedia); Books at Luther
Andrew Louth (Wikipedia); Books at Luther
Pauline Allen (Wikipedia); Books at Luther
Sean Freyne (books at Luther Sem)
Elaine Pagels (Wikipedia); Books at Luther
Frances Young (Wikipedia); Books at Luther
Dale B. Martin Wikipedia; Books at Luther
Martin Hengel (Wikipedia); Books at Luther
Judith Lieu (Wikipedia); Books at Luther
Also consider these select books by Susan Ashbrook Harvey, Alexander Treiger, Lewis Ayres, John McGuckin, Christopher Beeley, Lois Farag.
and this LibGuide on Antony & Desert Fathers and these other Early Church Fathers:
"Christians of the Patristic Period in Relation to Nature."
75 select, recent, full-text articles on Early Christianity from the ATLA Database: Early Christianity in ATLA Database
Historiography of early Christianity in Wikipedia
Open Access Digital Theological Library
A Sampling of over 500 theses and dissertations (full-text) from OADTL
JSTOR Access to Arts and Sciences III and the Religion and Theology collections
Some topics to explore using these online databases: For example, the subject of "Women in early Christianity" yields over 40k journal articles and 68k book chapters accessible in JSTOR here.
According to ChatGPT, "the study of early Christianity (up to ~600 A.D.) faces a number of complex issues across historical, theological, textual, and archaeological dimensions. Here are some major challenges and debates: 1. Scarcity and Fragmentation of Sources; 2. Diversity of Beliefs and Practices; 3. Relationship with Judaism; 4. Roman Persecution and Legal Status; 5. Canon Formation; 6. Christological Debates; 7. Archaeological Evidence; 8. Language and Translation; 9. The Role of Women; 10. Influence of Hellenistic and Pagan Thought."