'Secretary' is a bit comical(so smile)<br />
also try other media<br />
it's very rare to find erotica with a decent plot. "delta of venus" by anais nin is good but it is short stories and less explicit.
Have you watched both versions of the "Story of O"? Plus several follow-ons which are different but along the same theme.<br />
The 1975 film was well done for it's time but didn't satisfy true fans of the book. But the "series" (10 one hour videos) followed the book more closely. Both are still available.<br />
There are several movies that have a similar theme. Most are poorly done but may interest you.