The first book is probably the best stand alone, as it ends in a climactic battle against a foe that appears suddenly (though subtly) in episode 1. Plus it starts characters at first level, and that seems like a natural entry into a campaign.
The second book escalates the conflict, but it assumes that the players are already established heroes with a record of fighting Drow. If players are willing to accept this (and start at 11th level), then Book 2 should be no problem as a stand alone. More so than the first book, it features exotic environments (desert, seagoing, arctic, extraplanar) and earth-spanning action. It too features enemies that appear in the first episode to be challenged in the last.
The third book is largely a plane-hopping adventure that does not require completion of the first two. However, some old NPCs make appearances, and again players are assumed to have earned a reputation in the Drow Wars, so players without the experience of the first two books may be confused in places. Haven't played it yet, but it looks like great fun.
Check out the reviews on ENWorld, or visit my campaign website at
www.geocities.com/maddrmark/drowwarindex.html
We're only halfway through the first book, but we're having a blast.