Non-scifi series that end up being scifi David Bacaldi has a Jack Reacher knock-off called 'John Puller' who is an MP. There are four books in the series. The first three are straightforward murder-mystery/thrillers.

The four one is also a murder-mystery but then has a twist that is straight-up science fiction (I don't know how to spoiler code or I'd add the twist).

Any other on-going series that suddenly jump genre and become Sci-fi?