Update:
Whenever I try to edit the bookstore settings, I get this:
SplFileObject::__construct(/home/pewcatsm/public_html/templates/bookstore/style.css): failed to open stream: No such file or directory

Well this tells you that the theme has no style.css file. It is a problem with the bookstore theme, and its beyond what my support can offer. You need to contact the designer who made the bookstore theme.

Ah. Okay, thanks!

you are welcome. But anyway, its enough strange since I checked the header.tpl file for this theme, and dont find that its trying to load style.css file. This means the style is working fine, but something else causes the error on your site.

Update: I found that this is actually a problem with many themes, as you cannot edit the theme in ACP unless the theme has a style.css file. My recommendation is to not change styles through ACP, and instead edit it in FTP or your local file directly, then upload your modified files to your server to overwrite the old file.

I fixed it, on line 142 of the /bookstore/main.css file. I changed something. I can't find where to edit the text, however.

Well if you rename main.css to style.css, it will work for you. Although by doing this, you also need to change the header.tpl file to load style.css, not main.css. This is a minor issue though, as it states that only themes with style.css as its css file can be edited in ACP. Otherwise, you need to edit the theme by simply modifying its file content, not from ACP.

Okay. I HAS A MEMBER :D

Oh god what happened it stopped working

It deleted my body html for the bookstore theme. How do I fix that?

oh I see, congrats that you have a new member. And calm down, tell me what makes your site stop working? I visited your site as a guest and everything was normal.