I gave up on this, finally, and return it to the library after incurring $5.90 in overdue fines.
No reflection on Eco's seminal text; I'm just too busy to clear my mind and spend the many hours it was taking even to get through the 30-page Introduction. The intro felt like it pretty clearly encapsulated his Eco's post-structural approach—and was probably the only part of the book I had the intellectual background, to say nothing of the patience, to make my way through.
Eco's Six Walks in the Fictional Woods, which I found more lively, layman-ish and readable, is kind of a Cliff Notes version of The Role of the Reader. (I think. I mean I got far enough to suspect that, at least.) I found the former so provocative and foundational, or whatever the proper term is for something that provides the foundation ex post facto for everything you've read/learned up that point. Given that, and a few other brushes with critical theory that also pointed me to Eco in recent months, I look forward to returning to this (in a possibly mythical future) when I'm less harried and distracted.