Here are the stats from National Gaming Day at Your Library:

Number of libraries registered to participate: 1,365
Number of libraries that submitted number of players for NGD activities: 549
Total number of players for NGD activities: 31,296

For comparison, here’s 2008:

Number of libraries registered to participate: 617
Number of libraries that submitted number of players for NGD activities: 557
Total number of players for NGD activities: 14,184

Source has many anecdotes from the day’s activities.

(source)