If Schreker is someone you haven't quite investigated yet, but nevertheless a name hovering in the background of your musical life, EMI's new compilation can be warmly recommended at the price. Chandos is the main competitor but much more expensive right now.
The Chamber Symphony is an exquisite fantasy to be put alongside - contrastingly - Schoenberg's Verklarte Nacht. It's maybe just a tad too repetitive but rewards repeated listening, if only episodically. check out Simon Rattle conducting a taster on YouTube. Schreker's operatic 'preludes' are really full scale sonata reworkings of opera intros, thus explaining their duration. Again, the orchestration is luscious but never cloying, strong stuff, and very imaginative. The Romantic Suite and Intermezzo should be your first port of call if you favour Wagner and Mahler.
Listening to this, I wonder whether the so-called Second School of Vienna needs renaming, or new personnel. Perhaps it's Mahler-Zemlinsky-Schreker, or Zemlinsky-Schoenberg-Schreker? However you join the dots, the lost voices of the late-romantics of Vienna need to be amped up and this is as good a way as any.