Very fine soundtrack, very well done !
I can easily hear the Hotel Dusk/Last Window influence (especially in the last two track, with Discovery reminding me of So Noted, and Half Full, Half Empty having moments reminding me of Rachel's theme Serenity) and it worked out very well with your retro detective setting.
Speaking of influences, Midnight Rendezvous reminded me of Paradise (Stay Forever) from Paradise Killer (Nina from the excellent artwork from your album sort of reminds me of the protagonist from Paradise Killer also now that I think about it) so great to see !
Speaking more about the tracks themselves, all of them are very delightful with their jazzy ambient style, it really immerses you in this setting you've built, I really enjoyed it a lot.
My favourite tracks (if I had to choose) would be Discovery (very great melody throughout and nice variations throughout) and Half Full, Half Empty (with that very soothing rhythm and arrangements, very great work on that one).
Overall excellent work, congrats !