I use keywords, too, but I don't work with the Mystical Lenormand. That one is a bit closer to tarot than a Blue Owl, French Cartomancy, Piatnik - it has more in the pictures, where the cards I use are basically a symbol (ring, book, lady, whatever) with a playing-card inset.
The Mystical has more artwork. I checked in a German database (about all you can find on the Net), that has meanings for combos for several different Lenormand decks; sometimes the Mystical is a bit off to what you'll see in a typical Lenormand. But even with the normal Lenormands, there are sometimes differences because of is half the coffin covered, which way is the book facing, etc.
However you want to use it is fine, but there is quite a lot of tradition behind Lenormand reading. Not all the traditions agree, but they do all use card combinations.
With the Mystical, though, I think you're half in tarot-land and half in Lenormand-land.