Learn English – Explanation needed: Why is “and” wrong in this sentence

conjunctionsword-choice

It is difficult to predict what kinds of books will be popular in the years ahead, because tastes change and topics either get overexplored and lose their relevance.

I have placed the key words in bold type. Apparently, the word ‘and’ is grammatically wrong. Can anyone explain why?

Best Answer

When you use either, it should always be followed by an or and hence using and here makes it grammatically wrong.