We booked our trip through the official website, we were lucky to get tickets at all, the sell out very very fast, Alcatraz is the most visited tourist attraction in the united states which surprised us, and much more so after we had visited the island, most of it was closed of and of the parts that were open, some art exhibit had hijacked most of the space, and some of the buildings were being refurbished.

if you're going to visit the rock, make sure to book your tickets in advance or you may have to buy them from an unofficial site/from scalpers and they jack up the prices