A description can be hard to write for any author- how do you accurately tell a reader what your book is about while not giving too much information away? It can be tricky to find a balance between informing the potential reader what the book is about whilst still withholding a lot of information.

I always say that you need three things in your description:

1. Name and Setting. This introduces your character straight away and gives readers the context of book.
2. A vague outline of the general plot (not giving away any plot twists). I usually focus on the general plot at the start of my book because there aren't any major plot twists there. For example, if my book was about a crazy alien who crashed into earth but eventually falls in love with a human, my description would start off like:

'When Zozo crashes into Earth accidentally, she's left to fend for herself...'

3. A rhetorical question as it heightens suspense and makes the reader want to find out the answer to the question by reading the book. 

Descriptions tend to be short and concise, so don't make them too long however don't make them too short. Descriptions that are too short can put off some readers (of course description length varies between genres) as they aren't given enough information although there are exceptions to this.

Try to avoid making your description too complicated as this will confuse potential readers, and possibly put them off reading your book. Try and keep things simple and informative while still being descriptive and engaging.