I've lived in Calgary almost all of my life, and I can't believe I've never heard of this place.
My co-worker suggested our office venture to "the Shack" and bond over all we can handle crab. I thought this was a solid idea.
When I go to these "all you can eat" events, I expect high volume, mediocre quality. This is fair since their trying to keep up with serving our gluttony. To my pleasant, and maybe regretful, surprise the crab was consistently served hot and fresh. The servers were on top of keeping our buckets replenished. I recommend taking up Wendy P's suggestion below, and have a Beam Lemonade to wash down your crab.
I left with my pocket considerably empty and a goal of avoiding crab for a year. I would say Booker's did their job, and did it well.
Come one, come all to feast on crab like you've never done before.