Constantine, from the DC/Vertigo series Hellblazer. There's a big-huge wiki on him here for the curious. As per UTR, he's coming from after the Fear Machine arc, making him in his late 30s, although dreams will be slowly but surely catching him up with his life thus far (as of Feb 16, he remembers up until the end of Dangrous Habits, the 'parallel story' of the movie).

His journal is ~silkcutcasanova, his PB is Sting (yes, I'm so original) and his mun is Colleen.