Not enough people know about Cat Stevens, and that's a shame. But now you know, and knowing is half the battle.
While you're at it, you should check out Harold and Maude too. It's a film whose soundtrack is set entirely to Cat Stevens songs for one, so that's just fun. But it's much more than that. It's my favorite movie, for one.
For another, it's a movie about the very best kind of weirdos, how opposites attract, how individuals cope with the heavy burdens we bear for our country and our fellow man, death, and about living life completely on your own terms. Also, there's that gem of a woman Ruth Gordon and cute-as-a-button Bud Cort.
If you don't watch it, I won't judge. Old movies can be hard to watch. But if you like comedy and can suffer through the few cringy bits, you will be pleased you did.