Necromancer fan boy here.
No, it is not a must buy.
Its a good buy, but nothing is a must buy except the Core rule books.
I'm happy with it. Happier than I am with Worlds Largest Dungeon, which I got for $45.00.
Now if they would drop the pdf prices a little more I would be even happier, even though I already got those for free as part of the pre-order. I haven't actually received the pdf's. or a notification about them, but I am assuming the GenCon release, etc... is the reason this hasn't been acted upon just yet.