I think I read both this and Lord Valentine's Castle (though I think I gave up after the 2nd book on the world), as well as Dying Inside - which was pretty good, IMHO.
The novel's main character, David Selig, is an undistinguished man living in New York City. David was born with a telepathic
gift allowing him to read minds. Rather than use his ability for any
greater good, however, Selig squanders his power, using it only for his
own convenience. At the beginning of the novel, David earns a living by
reading the minds of college students so that he can better plagiarize
reports and essays on their behalf.
As the novel progresses, Selig's power becomes continually weaker,
working sporadically and sometimes not at all, and Selig struggles to
maintain his grip on reality as he begins to lose an ability on which he
has long since grown dependent.