At first I assumed @Joshua Ulrich meant the scans which were fine by me. First response with that knowledge below:
I've handled these flags, marked them helpful and made a comment on them:
Discussed this*, it's up to the holder to contact SE and I don't want to set a precedent. Furthermore, this might constitute fair use.
Note that we, the community moderators, can't be the final judge on this issue, we're neither qualified nor authorized. If the copyright holder wants this material removed he will have to file a DMCA request to the corporation behind SE.
Personally I don't see any ethical problems with this form of sharing the material: the source of the material is named and it can't be used instead of the original. Practically, I'd like to see a more condensed version of the same content (again sourced) so readers can digest and answer it more easily.
However, the user also linked to the complete book. This is discouraged. Please edit to remove and flag so moderators can take action against repeat offenders.
* In the moderator chat