If you'd like to read a pretty good science fiction book where the primary character fights using karambits, look for a copy of "The Musashi Flex" (it's the latest in the Matador series by Steve Perry). It was released in paperback late 2005, so may be hard to find -- you might need to buy them used online, but that entire series was worth reading. Of course, some in the series were better than others; my favorite was "The Man Who Never Missed".

While "The Man Who Never Missed" was the first published, from a story chronology standpoint, it's the third book -- "The 97th Step" was the story of the man who trained the main character in "The Man Who Never Missed", and though last in the series, "The Musashi Flex" is a prequel to "The 97th Step".