Slartibartfast's study is a mess because the cleaning staff all died, which is a real shame. For one thing, they have no one to clean up the dead cleaning staff.
But Slartibartfast can still find the Sens-O-Tape, which gives Arthur a complete sensory experience. It's like virtual reality, or Las Vegas.
In Chapter 25, the computer Deep Thought said it would take 7.5 million years to find the answer to the question of life, the universe, and everything. Now we fast-forward to the day when Deep Thought will finally answer the question.
There's a huge audience waiting in the streets for an answer. It's like New Year's Eve in New York, plus Mardi Gras in New Orleans. A speaker works up the crowd, noting that soon they'll have an answer and will no longer have to worry about why they're here.
Inside the building with the computer terminal, two computer programmers, Loonquawl and Phouchg, prepare to hear the answer from Deep Thought. There's a lot of suspense over this answer.
Deep Thought is a little hesitant about revealing the answer and tells them they won't like it, but they demand to hear the answer.
So Deep Thought gives them the answer to life, the universe, and everything. The answer is: 42.