You can.

But that doesn't always mean that you should.

I imagine that each book has trademarks and/or copyrights along with licensing,  as long as you follow those, then you should be able to post with the proper citation, just like if you were writing a research paper you would be bound by MLA or APA rules for Citation.   

Anything posted on Stack Exchange sites is posted under [CC By-SA 3.0][1] with [Attribution Required][2]

Most of the time if you cite the work properly, you can post it wherever you like while following [the advice you were given on your Law Post][3]

> - is what was taken an insignificant amount of the entire work?
> - is reference made to the original work?
> - is your work transformative, changing the original into something new?
> - is your purpose non-commercial, that is, not one aimed at deriving directly related economic benefits?
> 
> If you can safely answer "yes" to all of the above, you're safe.


Bottom Line:

Make sure to cite your source appropriately, or the post may be removed for violating the author's/publisher's right to attribution.

  [1]: https://creativecommons.org/licenses/by-sa/3.0/
  [2]: https://stackoverflow.blog/2009/06/25/attribution-required/
  [3]: https://law.stackexchange.com/a/28329