LOS ANGELES - "The Hitchhiker's Guide to the Galaxy" thumbed its way to the top of the box office, debuting at $21.7 million to beat out the explosive "XXX" brand.

Ice Cube's action tale "XXX: State of the Union" opened a weak third with $13.7 million, according to studio estimates Sunday.

"XXX" came in behind the previous weekend's top movie, "The Interpreter," starring Nicole Kidman and Sean Penn, which slipped to No. 2 with $14.2 million, lifting its 10-day total to $43.6 million.

Hollywood's pre-summer slump continued, with overall revenues down for the 10th-straight weekend.

Adapted from the first of the late Douglas Adams' comically philosophical books about the nature of our big, old goofy universe, "Hitchhiker's Guide" follows the adventures of an ordinary Brit who catches a ride with aliens moments before Earth is destroyed to make way for an interstellar bypass.

Critics soundly trashed the new "XXX" flick, but they also disliked Vin Diesel's original, which did more than three times the business over opening weekend than the followup.

1. "The Hitchhiker's Guide to the Galaxy," $21.7 million.

2. "The Interpreter," $14.2 million.

3. "XXX: State of the Union," $13.7 million.

4. "The Amityville Horror," $8.1 million.

5. "Sahara," $6 million.

6. "A Lot Like Love," $5.2 million.

7. "Kung Fu Hustle," $3.8 million.

8. "Fever Pitch," $3.75 million.

9. "Robots," $2.65 million.

10. "Guess Who," $2.2 million.