Mike Licona, Associate Professor of Theology at Houston Baptist University, has a helpful video on how we got the New Testament.
One caveat: He quotes Origen as having an agnostic position on the authorship of Hebrews but David Allan Black points out that Origen was really only agnostic about who actually penned the letter but the thoughts are from Paul. He says,
Origen meets the stylistic objection to Pauline authorship in a manner similar to that of his predecessor Clement: the thoughts are Pauline, but the style and diction are to be credited to another hand. In this way Origen maintains the apostolic origin of the epistle while removing the objection drawn from the diversity of style. When Origen says, “For not without reason have the men of old handed it down as Paul’s,” and then adds, “But who wrote the epistle, in truth God knows,” he does not mean to suggest uncertainty about the author but only about the penman—that is, the one who reduced the letter to writing—for he has just asserted that the thoughts are those of the apostle Paul. To assert (as is all too often asserted) that Origen meant to suggest that only God knew the author of the epistle is to suppose that Origen has contradicted himself in the very same paragraph. (Source)
The video is a great basic introduction to how we got the New Testament today. Check it out!