An update on my (joyful) trudging through v4 of La Grange's Mahler:
This will probably sound obvious to many visitors to the gustavmahlerboard: v4 is more suited for the scholar or "Mahler-nut" than for the general public.
You already knew that, but here's an example that brings home the point.
Henry Louis de La Grange does not, as many Mahler biographers do, write that Mahler was well-received in New York, and then provide a few quotes of critics or concert-goers.
HLDLG tells what nearly all the critics and significant people on the cultural scene thought of Mahler's premiere, AND what their backgrounds were, and their interactions with other society figures and the history of the atmosphere helping to form their opinions and attitudes.
In short, (and you probably already knew this!) La Grange does the most comprehensive job imaginable of telling the whole story of Mahler's time in America. It's not the sort of book most people would wish to read, cover-to-cover; it's an invaluable reference to rush to for the "definitive word" on matters Mahlerian.