The Benedictines being the primary monastic order of the Early Middle Ages, see: Clark, James G. The Benedictines in the Middle Ages. Woodbridge: Boydell, 2011.

The classic on the history of writing and documentation is: Clancy, M. T., From Memory to Written Record, England, 1066-1307. Cambridge, MA: Harvard Univ. Press, 1979.

A few others on the literacy/documentation side:

Gameson, Richard. The Early Medieval Bible: Its Production, Decoration and Use. Cambridge, 2009.

Clemens, Raymond, and Timothy Graham. Introduction to Manuscript Studies. Ithaca: Cornell Univ. Press, 2007.

/u/AerionTargaryen gives a pretty good start, but I would like you to clarify what you mean by "western civilization." Do you mean physical structures such as Westminster Abbey? Intellectual ideas from guys like Peter Abelard? As caretakers of documents in libraries? Modern holdovers of medieval institutions preserved through things such as universities and schools? All of the above? Some other kind of idea?

Here's a couple of books that cover some broad areas:

1. Charles Homer Haskins. The Rise of Universities (dated, but still a good introduction)

2. David Knowles. The Evolution of Medieval Thought (older, but you'd be hard pressed to find a better one that covers the same material)

3. Marcia Colish. Medieval Foundation of the Western Intellectual Tradition, 400-1400 (Yale, 1997)

4. Elizabeth Rapley. The Lord as their portion : the story of the religious orders and how they shaped our world (a general survey, but unsure of its quality)

5. Mary Carruthers. The craft of thought : meditation, rhetoric, and the making of images, 400-1200

6. Maximilian Sternberg. Cistercian architecture and medieval society (Brill, 2013)

7. Sarah Hamilton. Defining the holy : sacred space in medieval and early modern Europe (Ashgate, 2005)

8. Robert Wisnovsky. Vehicles of transmission, translation, and transformation in medieval textual culture (Brepols, 2011)

9. Jennifer Summit. Memory's library : medieval books in early modern England. (Univ. of Chicago, 2012)

10. Marcus Bull. Thinking Medieval (2005)

Hope this helps a little. Happy Reading!

How the Irish Saved Civilization by Thomas Cahill deals with that very topic. However, i do not know how accurate it is as I have not read it.