Of Lust and Lore (Lines 15-21)

Travel -- both for business and pleasure -- has kept me busy, so I apologize in the delay. That distinction is quite appropriate for this next stanza:

Of usage (what for luste what for lore)
On bokes rede I ofte, as I yow tolde.
But wherfor that I speke al this? Not yore
Agon it happed me for to beholde
Upon a bok, was write with lettres olde,
And therupon, a certeyn thing to lerne,
The longe day ful faste I redde and yerne.

luste/lore - pleasure/learning; yore agon - long ago

So now we have a glimpse into what's coming next: he's learned all he knows about love through books, but he's telling us about a specific day not so long ago when he found this book in Latin.

Note this is the second time in this very young poem that he's used the lerne/yerne rhyme. Previously, love was sliding so quickly away; now he's reading about it quickly. It's an interesting juxtaposition for our narrator, the reader.