1) You might relate what got you into classical music in the first place.
For example, a specific work or concert that you loved? That might help
pinpoint a direction to start from.

2) Did you pick your list with the intention of focusing on 20th century
works? As has been mentioned by others, this is a somewhat unusual starting
place, but there's no reason why it can't work for you.  But the "easier"
music is usually earlier (Classical and Romantic periods).

3) For piano, you can't go wrong with Bach (e.g., Goldberg variations),
Mozart piano concerti, Chopin (e.g, nocturnes), Debussy solo pieces; but
there's so much out there and everyone's tastes are different.

4) For "beginner" books, I liked Copland's "What to Listen for in Music"
and Bernstein's "Joy of Music" and "The Unanswered Question." (It helps a
little to be able to read/play music to really "get" these books, but it's
not necessary.)

Regards,

Richard Tsuyuki
Virginia, USA