The reason I bring up Alien is that the preface claiims that Van Vogt sued and won a "substantial amount" of money from the producer's of Alien on the claim that the movie was "derived" from the book.
Myself, I don't see it. Very few similarities other than an alien on the ship (and that's only the first third or so of the book).
Addendum (October 23, 2002): Well, now I'm replying to myself. How strange can that be.
On the bus home last night, reading Space Beagle on the Handspring, the soundtrack to Forbidden Planet comes on the MiniDisc (yes folks, it's a total immersion experience...anything to overlook the fact that I'm on the bus!).
I was reminded that I always thought that Forbidden Planet was a damn good filmed version of a lot of stuff that Van Vogt wrote about, especially Space Beagle.
But for some reason, the folks who did FP were never sued. I guess back in the 50's, when the film was made, nobody thought of such a unique idea!
Addendum: Space Beagle III
Well, mystery over the lawsuit solved. I had forgotten that Voyage of the Space Beagle is made up of several short stories. One of them involved a pretty indestrctible alien that gets on the ship and manages to "impregnate" several crew members by planting eggs into their stomach areas. Scenes involve chases through ventilating shafts, the crew attempting to escape via lifeboat and the like.
So it looks like our late, beloved author (A.E. Van Vogt) was justified in the lawsuit (or so I would say, if I were a lawyer).