Believe it or not, a "secret" society refers to the secrets they hold, not that the society itself is secret. The Masons are public about their existence (if quiet) but their inner "rites and rituals" are secret.
While I’m sure that used to the case, that is no longer really the case with the Masons. You can find out and read through all the different ceremonies and rites online.
Masons [have been known to] occasionally change certain things to keep known secrets to stay secret: 'letter and begin', for example.
Duncans Ceremonies is the most famous revelation of Masonic secrets, but no dues-card and not being 'in the book', ultimately counts for nothing, as you won't even be able to properly converse with a mason, nor enter a lodge, without either.