Nothing against the movie, by the way, which you should watch if you are interested in the field (it is just $4.99 on Amazon). The book by Ken Kesey is a must read.
Video clips such as these, which are often included in Instructors' Media DVDs that accompany Abnormal Psychology textbooks, don't help (the action starts around 1:06 -- seizure-inducing electrical shock without muscle relaxants):
The following clip is far more representative of "modern" ECT. I remember it made a big impression on me in grad school. "Mary" is an excellent case study in psychotic depression, the condition for which ECT is most effective. After observing my first "live" ECT, the attending psychiatrist asked for my impressions: "Uh...pretty boring, actually." "Exactly!" he replied. Psychiatrist, surgeon, pilot, etc. -- always opt for boring versus the alternative.
Shock Therapy by Edward Shorter and David Healy is excellent, and is probably the most authoritative word on the history of the convulsive therapies (there's insulin shock, as seen in A Beautiful Mind, and Metrazol shock as well). The book might be a bit more than the typical undergraduate psych major is looking for, but, as Lincoln said, "People who like this sort of thing will find this the sort of thing they like."
And finally, here's Sherwin Nuland, MD speaking about his personal experience with ECT: