There are a lot of articles appearing about Stephen Sondheim and it feels like every interview he ever gave is resurfacing. A lot of the interviews are the same interview, repeating the tale of how he gave a musical he wrote in his teen years to Oscar Hammerstein, thinking Hammerstein would produce it on Broadway and instead, Hammerstein said, "It's the worst thing I've ever seen" and proceeded to teach the young Sondheim how to do it right. But there are interviews that cover other ground and I'll try to point you to some of them in the coming weeks.
Here's a link to an article that Frank Rich wrote in 2013 that somehow escaped my notice then and since. It will tell you a lot about that extraordinary composer.