I sometimes get edits to review where the person making the edit has added in some details or sources missing from the original answer (or question, sometimes)
Are you aware that these changes are correct/good, approve.
But it may be about a subject that I know nothing about, so I have no idea whether the added information is accurate.
Is it up to me to determine the accuracy of the edit?
No, is not up to you. If you aren't sure, just skip the edit as there is not tomorrow. To approve or reject any of those edits, you need to know what's being talked about. If you don't know, then skip. If you do know (ie. your own answer) then you can reject/approve.
Sometimes it's added to an already-accepted answer, so obviously the added information wasn't necessary to the original poster, but may be useful to future readers. However, if it's not accurate, it could be misleading, and there is a good possibility that nobody will check it since the issue is closed.
"but may be useful to future readers" if you don't know if it really will be useful from a technical point of view, skip it. Suggested edits allows you to filter edits by tags, just review those tags that you feel confident about and forget about the rest. The OP is always notified of any suggested edit on their post, so they would know how to deal with it.
Now, edits on questions that change the meaning are a big no-no. Adding or removing information. Now, if you know that the information isn't relevant and could be distracting, again you should have knowledge of whatever is being talked about, approve it.