I played the suggested scales on a keyboard and found this quite interesting. The difference in terms of space in music between an octatonic scale and pentatonic scale was quite noticeable. You can hear the eastern melodic sound in the pentatonic scales.
I listed to several pieces (or parts of them) from the suggested listening. Messiaen’s Vingt Regards Sur L’Enfant Jésus was largely atonal, although the parts I listened too were quite varied in rhythm and timbre. The use of whole tone scales in Debussy’s Syrinx gives the work a quite spacious feel, in a similar way the pentatonic scale works, but producing a different result, less exotic but with a lovely timbre.
I also listened to Ravel’s Mother Goose to hear an example of quatal harmony and Hába’s Fantasie, which showed microtonality. This had the effect of very slight harmonic intervals and creating dissonant chords.