What is a good intro to "Mahler"?

I can't believe noone mentioned the Mengelberg recordings!!!??? There are in my book, 2 illuminative Mahler interpreters (owners). Mengelberg- who championed Mahler's music, and Bruno Walter who was Mahler's assistant at the Vienna Phil. If you like Mahler as it should be played, listen to any Mengelberg recording, such as.... the 4th with concertgebouw, the 5th with concertgebouw, and then Bruno Walter's 9th with Vienna which is nothing short of miraculous. They are quite different, I would say the Walter approach is slightly more catholic, but they both get the spirit of Mahler right.

I was referring to the adagietto. which is worth the price of admission. and honestly, it is the highlight of the piece for me, and I find the rest tiresome to both play and listen to unless I'm really in the mood.
another beautiful adagietto performance is in the movie "death in venice".