I got all the Darth Maul series, and I really liked it. Especially since I have a thing for blue twileks (don't judge me).
I started reading the Darth Vader series, but did not like how he got his ass kicked and had to resort to shenanigans to win. So I didn't actually buy any of those even though there were some cool covers.
Dunno whats not to Like. Vader when he is weaponless and learning to use his new body facing basically a Jedi Battlemaster, getting beat, coming back and using his superior strength in the Force and willingness to slaughter innocents to win. Can't get more Sith than that.