It is so hard to find a decent modern day hardboiled detective game (non Victorian era) for a solo player. This could have fit the bill with a good solo variant.
Solo variant that retains the flavour of the original would need to deal with hidden knowledge. The first way that springs to mind is as an app, which I think a good implementation could be done (for solo).
The other way would have to change how the game is played. Some means of digging through a deck to eliminate suspects, motives and places without needing to know what the right answer is. The accusation part would need to change too.
Yes, I'm totally with you that there aren't enough games with this theme! I can imagine a game like this that plays like the Arkham Horror LCG game!