Service Model -- I was a bit disappointed by it because I did really enjoy the start. I think one of the problems was that Uncharles* was too much of a robot to be a compelling central character. Even though Tchaikovsky's playfulness and cleverness are there (well, they're visible in the Wikipedia summary I've just read to bring back my memory of the book), the unemotional, task-queuing driven narration sucked the life out of it.

* written as an actual robot rather than an autism analogue like Murderbot