This book was so full of angst. I think of it like a much calmer version of Forgive Me, Leonard Peacock in that way, although this is not the story of a kid thinking about murder/suicide. It does, however, have a mental health focus.
I am not familiar with the musical to be able to compare the two, but in its own right this is a wonderful Ya novel about feeling alone and invisible, even in a crowded room. It's about friendship and the hardships of life. I feel like anyone can easily relate to the novel, even if they haven't been in Evan's exact situation.