U.S. humanities professors: Can you get back into academia if you leave? I'm a tenured professor in a humanities department at a second-tier research university in the United States. My Ph.D. is from a top-ten program in my discipline. I have an above-average number of publications for my age.  I have about five years of undergraduate and graduate teaching experience post-Ph.D.

I have an opportunity to take a job as a writer/editor for a marketing company. I'm inclined to take it (for reasons I won't detail here) but am worried that if I don't end up liking my new job, it will be impossible to get back into academia after having left voluntarily.

I'm not expecting that I would get my current position back, or necessarily be rehired to a tenured position. I'm just wondering how hard it would be to go back on the job market and find a tenured or tenure-track position somewhere in maybe two or three years' time if I end up hating the new job.

I want to emphasize that I am in a humanities discipline. I gather that in the sciences, it is common for one to leave an academic position to go work in "industry," then later return to academia. I have never heard of anyone doing this in the humanities, however. Does it happen?
Speaking as humanistic social scientist at an R1 (but who has also taught at small liberal arts colleges), I would say it would be next to impossible.

There is an absolute surfeit of stellar recent PhDs in the humanities. Any position that opens up will get 200+ hungry applicants. Why hire at the associate or full level if you can get a stellar assistant at a quarter of the cost.

Furthermore, if a senior position did open up and a search committee were to look at your CV, I would think they might wonder whether you left academia because: 1) you were pushed out (sexual harassment? Title IX violation?); 2) were burnt out of teaching; or, 3) something else unmentionable. If you left because you hated academia, why are you trying to get back in? Academic hiring is risk adverse because of the stakes of tenure. 

However, as an alternative, you might be a candidate for some peri-academic positions such as the director of an institute, dean of student affairs, etc.

tl;dr: Talk to your provost or dean or chair about taking an unpaid leave of absence that retains your tenured position.