Explain James's argument for God. Is it a version of Pascal's wager? Is it sound? Why?

I assume you're referring to his work "The Will to Believe"; in which case, he doesn't make an argument for God, really. What he says is that we can be justified in some beliefs *without* argument/evidence. James actually criticized Pascal's Wager, and rejected doxastic volunteerism. "The Will to Believe" is sort of a precursor to the work of Alvin Plantinga and his "Warrant" trilogy.