I'm 50 pages into the German 1977 Suhrkamp edition and finding it a bit of a pretentious pain in the donkey. Does it get any better? Is there a better, more recent biography?
Give it a chance. It gets better around p. 783.
I thought it was engaging, but whatever.
It's very much of its era, focusing on the manic, irreverent Mozart. There is Gutman's "Mozart, A Cultural Biography" and Maynard Solomon's "Mozart".
I have Bernhard Paumgartner's encyclopedic "Mozart" (the 1945 edition of the 1927 original), all 551 pages of which explore all aspects of Mozart's life and music. It usefully includes a detailed index of all his works - in which I discovered that at the age of 9 or 10 he composed what is apparently his only vocal work in English, a motet "God is our Refuge" KV20. He was on tour in England in 1765, so that must be the reason for it being in English.
I would recommend "Mozart in Vienna 1781-1791 by Volkmar Braunbehrens. It is available in English translation and offers a fresh take on Mozart's final decade - also some very interesting material on life in Vienna (and Austria generally.)