At least 25 stanza's of 4 lines each comprise the complete poem. The existence of a chorus suggests that it was originally sung as a ballad.
The most commonally quoted lines are as thus:
"The spirits white as lightening
Would on my travels guide me
The stars would shake and the moon would quake
Whenever they espied me.
With a host of furious fancies,
Whereof I am commander,
With a burning spear and a horse of air
To the wilderness I wander.
By a knight of ghosts and shadows
I summoned am to tourney
Ten leagues beyond the wide world's end-
Methinks it is no journey."
Robert Silverberg has written a book by the same name, "Tom O'Bedlam" (1985).