From what I know he wrote a few letters stating he planned to study Kierkegaard, but I imagine it was fairly limited. Either way I think it's interesting to see how much overlap each had despite operating on opposite ends of the spectrum with respect to religious faith.

I think the fact that the man singlehandedly started existentialism is enough to justify reading him. The problems we face in modern today (depression, suicide, anxiety, isolation in spite of connectedness) were all predicted by Kierkegaard. If you want a good and highly relevant place to start I would recommend his short book "The Present Age".

I'm taking an Existentialism class at my university atm and it's quite astonishing how every single philosopher of existence (Dostoyevsky, Nietzsche, Heidegger, Sartre, Kafka, Camus, De Beauvoir, etc.) has read Kierkegaard. His influence speaks for itself.