Oh I like your theme of not everyone having a happy ending! That really grounds people in reality, I feel.
And thank you so much for mentioning my novel! That makes me really happy, I appreciate it!
Since Devil's Triangle is mentioned, I might as well add that the themes in that novel are:
1. Technology is a double-edged sword
2. Ways to not parent your kid
https://tapas.io/series/Devils-Triangle
For Shackles, it would be:
1. Duty to the country over personal interest,
2. Breaking the shackles of your past.
And for Dark Bytes, the collective theme is:
1. Future uses and abuses of technology
2. The rebirth of humanity