Over and done with

[larryhammer]

For all his appealing writing, Edward Eager has several readily parodied mannerisms. janni and I wrote this back on GEnie:

          It was then that Eliza realized Jack was right and there was something to teenage girls after all. And if you have ever liked a teenage girl yourself, you know exactly how she felt.
          It was but the work of a moment to undo Lady Samantha's bodice, but the corset presented more of a challenge.
          "Oh, I wish the beastly things had never been invented," Eliza cried.
          And since this was a good deed, the magic relented.
                                    -- from Magic or Else

ETA: Something I only noticed last night, however, is that some things are but the work of a moment, while some are the work of but a moment. Hmph.

The remaining answers to twenty lines:

"Because many of them are thirteen stories high"
"Jottings of New York: A Descriptive Poem" by William McGonagall. This was the joker of the pack, because anyone with an ounce of sense tries to forget every line of McGonagall they read.

"The City is of Night, but not of Sleep"
The City of Dreadful Night by James Thompson, a Victorian poet. A poem that ought to be better known than it is -- a guided tour of the geography of depression and despair that's the prototype of Lankhmar.

"This is the parting that they had"
"The Haystack in the Floods" by William Morris. This is the penultimate line, leading to "Beside the haystack in the floods."