A student is stuck in the long, anxious hours before an exam. The speaker has spent a week on "fun and games" and is now trying to squeeze everything into one night with the books. The poem captures that familiar dread of time moving strangely: minutes crawl, then suddenly turn into hours.
The mood is tense and tired. Staring at "the same words over and over" suggests that the studying isn't working, and the speaker's hand trembles from exhaustion and nerves. Even the thought of sleep brings no relief, since the worry about falling asleep is just another source of stress.
The ending is the sharpest moment. Instead of the usual image of counting sheep to drift off, the speaker is "counting bones," which feels a little darker and more uneasy. The judgment of the poem seems to be that last-minute panic costs more than it gains, leaving the speaker both unprepared and unrested.