First of all you need Inscription(350 skill) And lvl 72+
Then go to Grizzly Hills Silverbrook Village and farm Silverbrook Villager and Silverbrook Trapper as they have highest chance to drop the book.
You are going to farm Technique: Rituals of the New Moonit will probably take you 10-60 minutes.(Note you must be Inscriptionist so it can drop)
After you get it, learn it ofcourse.
Now this is server depended.(Mats are not expensive. On my realm mats cost 50gold per book) .
For each book you need following mats:
5x [Ink of the Sea] to make one you need 2x[Azure Pigment] which you get from milling Northrend herbs.I recommed you to check following on Auction house.
[Adder's Tongue] 10g20s-13g80s
[Goldclover] 6g40s-9g40s
[Tiger Lily] 5g60s-9g
[Deadnettle] 7g20s-9g60s
Those are prices on my realm.
By my calculations each stack should give you around 13-18 Azure Pigment's
Another thing that you need is [Resilient Parchment] Each Resillient Parchment cost 50 Silver's each. They are sold by vendore near Inscription Trainer. Each book needs 10x Resillient Parchment's. So its equal to 5gold.
And last thing that you need is 3x [Eternal Shadow] .
You can either farm them or simpler buy it from auction house.
Each Eternal Shadow cost 12 gold on my realm.
So in total you spend 51 gold. You can sell each book from 150 Gold-300 Gold, so you are getting 150% minimum you have spent. Also when you put books on Auction House try to spam a little in trade for example.
Selling [Rituals of the New Moon] xxx gold each. In all colours. You will notice that people actualy buys it. Have fun guys and good luck.
Also don't forget its very Server Depended.