Best: This is a bit of a cop-out, but probably all three of John Green's novels.
If you really want me to choose three novels by unique authors:
1. Paper Towns by John Green. It had the perfect balance of romance, comedy, and angst, and the ending got me teary-eyed.
2. The Hitchhiker's Guide To The Galaxy (the first one) by Douglas Adams. Does this one even need an explanation?
3. Probably Stargirl by Jerry Spinelli. It's another one of those books that always makes me choked up...I need to read it again sometime, it's been a while.
Worst: Honestly, I've read a lot of bad books, but here's three, in no particular order.
1. The True Confessions Of Charlotte Doyle by Avi. I read this book in sixth grade because the plot looked interesting, but it turned out to be one of the most unrelentingly boring books I've ever had the displeasure of reading.
2. Twilight by Stephenie Meyer. Now, to be fair, it probably doesn't belong on my Worst list--I found it really addictive, and something of a fun read--but the fans are idiots and Bella and Edward's relationship is downright disturbing.
3. The Wild Kid by some person whose name I'm too lazy to look up. This one might also work on the Best list, since it's kind of so bad it's good. Basically, this kid with Down's Syndrome gets lost in the forest somehow and winds up surviving because of this kid who's been living in the forest for some time. It's poorly written and stupid to the point that you almost wonder if the author wrote it as some kind of elaborate joke. I'd recommend it to anyone who wants to laugh at really bad writing, but that's about it.