Each collector has his own priorities, Jim, but quite a few of us think full books are considerably more desirable than partial books or covers alone. They represent the artifact as it was originally made and are better representatives of what the gambler received from the casino, just as with unused chips. Agreed, they are harder to find in excellent condition and take up more space in the collection but that's one of the reasons they are more valuable.

I believe full books, at least in the casino speciality, are 50-100% more valuable to the collector. Full is the operative word; if I get one with matches missing, I generally turn it into a cover by removing the remainder.