The General Prologue of this amazing collection of stories gives us a very clear picture of this character and the way that he is so obsessed with books and learning. We are told that he has shunned the materialism of the world in exchange for the delights of books and learning, and certainly his physical appearance seems to support this impression:
The horse he rode was leaner than a rake,
And he himself, believe me, none to fat,
But hollow-cheeked, and grave and serious.
His rejection of the material things in the world is thus supported by his physical appearance and the lean and hard appearance of both himself and his horse. It is as if he has sacrificed all the pleasures of living and deferred his life so he can more focus on his books. Note how Chaucer concludes his section on the cleric's character:
He never spoke a word more than was need,
And that was said in form and decorum,
And brief and terse, and full of deepest meaning.
Moral virture was reflected in his speech,
And gladly would he learn, and gladly teach.
There is a deliberate note of irony in the final line, as it is infered that although he may "gladly" share his learnings with those around him, the "moral virtue" of which he speaks might not be so enthusiastically received as it is shared. The Oxford Cleric is therefore presented as something of a dull character, who deliberately cuts himself off from experiencing life so that he can focus on his study.