For my clients who've taken interim executive positions a little outside their area of expertise, quickly whether they want it or not becomes apparent. But typically regardless of the answer, they want to do a good, if not great, job.
CEO's have different groups of stakeholders - many of them external to the company, e.g. shareholders, investors, analysts, market makers - and they are great at spotting exceptions (pos or neg). I had a client dive into those groups and find they really enjoyed it and others that ran running back to operations, marketing, or finance asap.
Suggest you approach it like social anthropologist - dive into the role for a while, build your coalition of support & informants(!), try to get some quick top or bottom-line wins - perhaps based on your previous expertise - and try to find something new, outside your comfort zone (perhaps the entire experience is, so it'll be easy!) to partner on where you can develop a track record in strategy or with the analysts or market watchers.
That way you'll have developed something and gained some track record whether you decide to remain or to move on. Then you can truly say, it was a most valuable experience.