Having recently retired after 26 years of teaching high school and
college classes, I feel I can take a stab at this.
I have always _encouraged_ my students to read plot summaries.
Furthermore, I sometimes actually showed a movie (gasp) of any work we were
studying.

Teaching literature to a generation brought up not reading is a
challenge. If you can show them that what you expect them to read is
actually
interesting, then they are much more likely to read it.  And if you
can't help them make the actual assignment more interesting than a movie or
_Cliff's Notes_ then you need to reconsider your own abilities.
Besides, I frequently found that even a bad plot summary could help me
prepare to teach a class.
I believe the truly lazy student might try and get by with just a plot
summary even if the teacher is doing a great job.  On the other hand,
that student probably wouldn't read the assignment anyway, and a little of
something is better than nothing.
It's a simple matter to ask test questions or make written assignments
which require reading the material to know the answer.  I found after I
started encouraging reading summaries and occasionaly showing a movie, the
number of students who read the assignment actually increased.
As for the plot summaries in _MTAZ_, well, my compliments to the chef.
They're outstanding.

Jerry Salley