When I was studying this, the best sources I found were:

The Canon of the New Testament: Its Origin, Development, and Significance by Bruce Metzger

https://www.amazon.com/Canon-New-Testament-Development-Significance/dp/0198269544/ref=sr_1_1?ie=UTF8&qid=1497034222&sr=8-1&keywords=the+canon+of+the+new+testament

and

The Canon of Scripture, by F.F. Bruce

https://www.amazon.com/Canon-Scripture-F-Bruce/dp/083081258X/ref=sr_1_1?ie=UTF8&qid=1497034279&sr=8-1&keywords=the+canon+of+scripture

They are both Protestants but I didn't notice any particular theological bias. Both cover both the OT and NT but since we know a lot more about the formation of the NT, it gets a lot more coverage.