well, not sure what grade 12 equates to ( had different school system) im guessing 12 years of school?
If so, even then its hard to suggest a book with your description
More info would be welcome: ( e.g - how much you usually read, are you iso a book thats easy to read and interesting so its easy for assignment, or can it be more complex? )
well, anyway, here a few suggestions ( if you still need):
-To kill a mockinbird ( cultural impact, lots to talk about)
-Painted House ( good topics, quite an easy read while maintaining some substance)>> quite possibly best option from my suggestions
-Eragon ( or either sequel) >> just a hash of other fantasies, but its a very easy read + fantasy ( which you say you like) >>interesting subject for presentation,
author wrote book when he was only 15 years old, gives you a good starting point to discuss his literary prowess vs age
If you up for bigger books i would recomend ( depends on how much time you have/how fast you read)
- Tommo & Hawk >>> ( quite long) but very good narration techniques the author uses, alot to choose from for presentation
-The Physician >> excellent book, a must read anyway ( but again, very long, might put you off) >>> no shortage of substance to discuss.
If you really lazy ( and have a lenient teacher

) :
- The old man and the sea >> very short, but if you do a quick-ass presentation you can pull this off
Take advantage of the classic status this book has, the thousands of discussions/critical reviews this novel has had and come up with a original way of presenting it, you will save time reading, use that time for the presentation, alot can be said in 10 mins if well planned out

( if you opt for this one ofc.)
Hope this was helpfull, if you like/need, i can suggest a few more