I think it's been 15+ years since I originally read the story, and I believe it was either a short story or a fairly short novel. I recall certain tidbits like:
- The man's brain is put into a new "generic" body.
- His mental faculties are greatly diminished at first, so he's given an intelligent brain implant with eye interface that demonstrates with simple animations how to do simple tasks. The eye interface is activated by a couple of quick blinks.
- He spends the first few months doing menial labor of some sort, and feels like he is a captive or slave.
- He eventually escapes with the help of his brain/eye implant. One part of the escape that stands out is that he's screened at some sort of security terminal and asked why he has the implant, which the implant then tells him to respond "because I'm mentally retarded" which surprises the protagonist enough to make his lie sound believable.
- It's eventually revealed that his captors/masters awoke him to inherit some sort of great authority or power, once he had sufficiently recovered.