As if it could have ended any other way, Amazon managed to once again set sales records this holiday season. Amazon announced on Thursday that more than 1 million Amazon users became Prime members during the third week of December, and on the biggest shipping day of the year, more Prime items were shipped than any single day in the past. Amazon customers also ordered more than 36.8 million items on Cyber Monday alone — a jaw-dropping 426 items per second — including more Kindles than ever before. How many Kindles, exactly? We still have no idea since Amazon refuses to share any actual numbers. But speaking of tablets, Amazon says that more than half of its customers shopped using a mobile device this holiday season.