The full collection of The Hitchhiker's Guide To The Galaxy series, this collection includes the five Hitchhiker's Guide novels and a short story:
1. The Hitchhiker's Guide To The Galaxy
2. The Restaurant At The End Of The Universe
3. Life, The Universe And Everything
4. So Long, And Thanks For All The Fish
5. Mostly Harmless
6. Young Zaphod Plays It Safe (a short story)
It is one of the funniest series, and one of my favorites, ever. Read it now - it's got good writing, great jokes, and the meaning of life thrown in. What more could you want?