For studying the format of quizlet is extremely useful. But unfortunately, once you make a quizlet account, you are screwed, because they will NEVER EVER STOP SENDING YOU USELESS EMAILS. If you don't have a quizlet account, you are fine to keep using it offline. An account is not necessary. I made the mistake of creating an account and now I am using it for school and cannot delete it. Please know that I do not hold anything against quizlet or its creators, but I think that whoever is in charge of the email distrubution went a little overboard.