His Norton Lectures at Harvard were fascinating too. They were more theoretical. e.g. https://www.youtube.com/watch?v=r_fxB6yrDVo Starting around 20 minutes he describes some of Chomsky's transformational grammar with examples on the piano.
Bernstein's "Young People's Concerts" taught me more than school ever did on music: highly recommended to at least try to get into/get your kids into. (They seem unfortunately dated now, even though the sound still hold up well). Example: https://www.youtube.com/watch?v=rxwWlQNGeKE
A bit of fun: https://youtu.be/qwYQwgtXSvc
"Take my seat aboard a plane and what is this I see?
Leonard Bernstein comes aboard and sits right next to me.
First class New York to LA some things just work out right.
I’ll be sitting next to Leonard Bernstein this whole flight.
Maybe I should just act like I do not recognize him?
Be real cool and do my best not to antagonize him.
Now we're rollin' down the runway, next stop is LA.
I'm nonchalant like I ride next to Lenny every day..."
For those of you in the Philly area, they are doing a nice exhibit on Bernstein at the American Jewish Museum.
I'm always reminded of the documentary following the recording Bernstein conducted of West Side Story with various opera singers.
The tension between him and Carreras that rises to a crescendo is awful and compelling at the same time.
>There's a book I recommend that is a compilation of most of Glenn Goulds letters, they are incredibly beautifully worded.
Care to grace us with the title of this book?
Glenn Gould: Selected Letters 
One should read the correspondances between Glenn Gould and Bernstein, they are very deep. There's a book I recommend that is a compilation of most of Glenn Goulds letters, they are incredibly beautifully worded.
Bernstein helped motivate me towards classical piano more than anyone. Watch his "The Unanswered Question" series as well.