Early Christianity was timed very well to come into existence. In an age of prosperity (relative to historical standards) distinctively marked by personal religion and popularity of the mystery cults, Christianity had very fertile ground. What might be overlooked is how budding technology contributed to the spread of Christian doctrine. One major development that helped spread early Christianity was the advent of codex. D.C. Parker describes codex as such:

In its simplest format, a codex is made by taking a pile of sheets of writing material, folding them in half, and then (starting at the top of the first sheet) writing the text on them. The whole pile is then stitched together through the centre fold.

Prior to the advent of Codex, Christians would have needed to use unwieldy rolls to communicate ideas via the written medium (other alternatives being wax tablets and wood planks which were not particularly suited for mass distribution). Codex started to become vogue in the second half of the first century. Paul explicitly says he owns his very own (2Ti4:13 “parchments”). D.C. Parker relates his translation of one advertisement for this innovative product:

Since you want my booklets with you
Round the house and on the road,
Buy these compact parchment tablets:
Leave the book box with the rolls;
Hold this in a single hand!
So you know where you can find them
I will tell you: seek Secundus
freedman of the Luccan savant
Behind the gate of Peace’s Temple
And the marketplace of Pallas.

This comes from the Roman author Martial who lived between 40-105AD, indicating codex had not universally replaced rolls at his time and was even then needing to gain marketshare.

Martial lists the benefits of codex. Codex was a smaller format that could be held in the hand and carried about on trips. It was more durable and even cheaper to produce. It was an amazing innovation that brought a literary revolution, at least in the Christian sphere.

Codex is the format exclusively found for all early Christian writings. Here D.C. Parker describes the state of existing manuscripts:

We have no copies of early Christian writings older than the middle of the second century, so we cannot at present know at what stage the codex replaced the roll, or even whether the codex was used for some or all of these writings from the beginning. The evidence of the forty or so manuscripts surviving from the second and third centuries is that by about 150 it was normative for Christians to copy the writings which later became the New Testament into the papyrus codex format.

If any book of the New Testament was represented on rolls within the first century, we have no evidence of this fact. Instead early Christians most likely read exclusively from Codex. The mere presence of the codex lends itself to suggest a wider literacy for early Christians than suggested by Bart Ehrman (the author quoted by Ehrman for his less than 10% literacy claim says his estimate may not be in the same ballpark). The codex, like the Guttenberg Bible and the internet afterwards, represented literature for the underclass, literature to the people, easy to distribute and cost effective. Paul himself encourages wide distribution (reproduction?):

Col 4:16 And when this epistle is read among you, cause that it be read also in the church of the Laodiceans; and that ye likewise read the epistle from Laodicea.

Granted, wax tablets and wooden planks could have been used (both of which would not even conceivably last until the modern day), but most likely this was to be reproduced on codex (durable, relatively cheaper, and easy to handle). Without the codex would we have Christianity in its modern form? Most likely not.