I read a really amazing book recently which perfectly blended science fiction and M/T and while reading, I realised that there were certain aspects which I could pick up and make into tips.

The main thing I noticed was that there was equal influence from both genres. It wasn't a Science Fiction book with some M/T aspects or a Thriller book with a bit of SciFi chucked in. In each chapter, there was equal mention of the SciFi aspects as well as the the M/T aspects.

Another thing- it makes it easier if you set the book in modern day Earth. That way you don't have to explain a whole new world in a book that is already action packed and confusing as it is.

These two genres work SO well together as some writers may find that their SciFi idea may be lacking something SPECIAL. What's more interesting than a serial killer alien who is mutating humans and the police can't find them?