Do you know how to use semicolons, where to put your apostrophes and when to use commas? Do you know the difference between affect and effect, if and whether, or who and whom? (Does anyone still say whom?) More importantly, do you know why this stuff matters? The truth is that if your writing isn't up to scratch, it just won't be taken seriously. So, if you've reached a stage in your career or education where your writing needs to be high quality, Grammar Rules is a must for your top drawer.