The wheel was awesome (and still is)! I actually have two copies. On one the wheel came off, but it was easily remounted with a paper fastener.I have to confess, had I been a fan then, a book with some archaic wheel mounted reference system built into the front cover (itself designed like a starship dish) I would have loved it.
I can't speak to any later edition, but the one pictured was outstanding and invaluable. Today, it's surpassed by Memory Alpha and other online references in their breadth, but the Concordance set a benchmark to be met.