I had stated to my friend that i was going to watch this show, they told me that i should stick to the first ten episodes of season one and then book of circus because those were allegedly 'canon' but knowing my nature to watch a show all the way through, i watched both all of it.
Now there were multiple problems, when i started i was expecting something dark and gruesome. Not a fabulous butler that tends to the whims of a bratty piece of shit kid. Now keeping in mind, i would be a bit irked if my parents were killed and i was forced into being a part of some satanic rituals or whatever they did to Ciel Phantomhive. But that's no reason to be a piece of shit the entire time.
I would not recommend this to anyone. it was a waste of my time. but don't let that bar you from watching it.