Well i think i probably haven't added anything to what the other have wrote but actually here are some of my thoughts about the anime

This anime contains almost everything needed, it has a good and captivating story-line. It stays on the story-line in every show and has its good combination of sci-fi, romance, comedy and mystery. the proportions of these factors are chosen in an expert way which makes this anime keep you watching it till the end while keep you guessing from time to time.

I felt like it had a little slow start but i'd say it doesn't affect the richness of the series.

This anime is actually one of my favorite one. and i hope to see if they make a second one. but chances seem pretty slim.

Oh and a personal request please if any of you know some good anime specially in Sci-fi and mystery a reply would be very much appreciated