Don't use THEIR to signify gender neutrality
How people commonly misuse THEIR
O'Brien effectively causes the reader to change their view of John Wade.
Why is this wrong?
The problem is with pronoun agreement. THEIR is a plural pronoun. It is the possessive form of THEY. Because THEIR is plural, it doesn't agree with the singular noun, READER.
Why do people do this?
Usually people make this mistake because they don't want to write "his," they don't want to write "her," and they don't want to write "his or her." They use "they" or "their" to sort of cheat and avoid dealing with gender altogether. You just can't do that, though, because as I said above, you can't use a plural pronoun to refer to a singular noun.
What are my alternatives?
If you want to keep the noun as READER, then you must pick HIS or HER for the pronoun. If you want to be extra-politically correct, spend one paragraph using HIS, and then switch to HER for the next paragraph. Don't write "his or her." It's awkward and wordy and would give E.B. White a heart attack. Pick one pronoun and run with it for a while.
OR, you can flip the whole thing on its head and change your noun. READERS works perfectly well with THEIR, because they are both plural.
OR, you can flip the whole thing on its head and change your noun. READERS works perfectly well with THEIR, because they are both plural.
BOTTOM LINE
Always make sure your pronoun agrees with its antecedent (the word to which it refers).