Dirk Gently

1. Dirk Gentley's Holistic Detective Agency
2. The Long Dark Tea-Time of the Soul

Note: The Salmon of Doubt is a collection of writings published posthumously, including a few chapters of the unpublished third book in the Dirk Gently series

The Hitchhiker's Guide to the Galaxy

1. The Hitchhiker's Guide to the Galaxy
2. 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. And Another Thing... (written by Eoin Colfer)