Here's why Grammar is important:

1.) A professional book would have perfect grammar. If you want to be the real deal, your book needs to have the same.

2.) Bad grammar ruins the experience, especially for older readers who understand the rules of writing better. Bad grammar is probably the biggest turn off for a reader.

3.) Bad grammar often signals to the reader you are new to writing and thus your book is less likely to be a good, polished piece of work.

What to do:

1.) Make sure your book description and first chapter is PERFECT! If you are not sure, ask someone who is good at writing to check it for you. This means a new reader is more likely to give your book a chance and might get hooked in by the first chapter.

2.) Try and do the same for the rest of the book. It's always good to have someone read over it and spot the mistakes before you upload, but make sure you read it over again after you finish the chapter. You will be surprised by what mistakes you pick up!

Oh yes, don't forget to vote :P.