(Listed in approximate chronological order that I read them):
1. The Hobbit
2. The Lord of the Rings
3. The Gammage Cup
4. The Black Cauldron
5. Sir MacHinery
6. Starship Troopers
7. Glory Road
8. Citizen of the Galaxy
9. Have Spacesuit, Will Travel
10. Hitchhiker's Guide to the Galaxy
11. Another Fine Myth
12. Guards! Guards!
13. Wee Free Men
14. What Your Mother Couldn't Tell You and Your Father Didn't Know
15. Passionate Marriage
Some of these are listed because they're in a series that I love, such as "The Black Cauldron" and "Guards! Guards!", rather than being the one book of the series that stands out.
Perhaps later I'll post "The Books I Realized I Should Have Included In This List That I Didn't Think Of Until After I Posted It."