I think this would be a safe bet with 99% of tech ceos. but in the tech won't save us series on musk there's an audio clip of him talking about hitchhiker's. and it seems pretty clear that

1 he did read it

2 he does admire it and think of it as informing his goals

3 his understanding of the book is that it's haha funny but on a deeper level it's saying we should do things like build giant planet sized computers. also something about weed