I love it. I love his snarky, no-holds-barred writing; I love his humble honesty; I love his casual mentions of other Russian greats; I love his glimpse into the brutality of Stalin's reign. He's not my favorite composer, but I respect his music more now that I understand that it was partly his muffled rebellion against Soviet constrictions.
The veracity of Testimony has been questioned, but embellished or not - it's a great read. If you have even the slightest interest in Communism, Soviet Russia, or modern Russian music, you should check it out.