While Pew listed the non-religious at 19%, Harris pegs it a little bit higher. They show the percentage of non-religious Americans as being 23%. That's 11 points higher than what it was just a few years ago (in 2007), and corresponds with a similar drop of 11 points in those who say they are very/somewhat religious (from 70% to 59%).
This same move toward a more secular country is reflected by a drop in the belief in a god -- from 79% in 2003 to 68% in 2013 (with 54% being absolutely certain there is a god and 14% being somewhat certain). Currently 16% say they are certain there is no god, while another 16% say they don't know whether god exists or not. There has also been a drop in the belief that religious texts are the "word of god". There is not a majority believing that any religious text is the word of god -- including the christian texts of the old and new testaments.
And belief in other religious ideas (such as heaven, hell/devil, deity of Jesus, virgin birth, resurrection, a soul that survives death, and creationism) have also shown a drop in belief. The only two beliefs showing a rise in percentage believing them are evolution and reincarnation.
The most surprising thing for me was how small the percentage was of those who are certain of the existence of god. Only slightly more than half of all Americans (about 54%) are convinced of god's existence -- and when the question is broken down demographically, there are several groups where that belief falls below 50% (see chart below).