About the story:
What happens if you die? Angel Beats! shows one of the many options. Going to a place where you make yourself happy and ready to go to the next stage. The SSS is mostly going on adventure with the new guy, Otonashi. He encounters sad, fun and other things. But the core of the story lies with the relationship between Otonashi and Kanade.
About the animation:
P.A. Works did a good job when it comes to the animation. Watching Angel Beats! in HD is like giving your eyes drugs.
About the sound:
There are not many sound involved. But when there is sound, it's amazing. Hearing the sounds makes you feel like you are sucked in the Anime itself.
About the characters:
There are different kind of characters. From shy one to an expressionly one. These characters does not develop in the series. But nevertheless they already have experience a lot of things.
Why overall a 10; The ending was so tearjacking that even an alien would cry. Everyone hopes for a second season and when you watched it, it will stay in your top 5 animes.