Rock/pop John Denver: "It's About Time." (RCA digital AKC 1-4740) -- Denver can write good songs -- there's no doubt. And he's not afraid of being sentimental, or of putting his own deep feelings in his lyrics. This album is a fine example of this, and the title track here is a humane, timely message about peace and the unity of mankind. At the same time, the song seems just a bit preachy. "World Game," Denver's trip into the land of reggae, is another song with a statement, this one on ". . . using less and/ Doing so much more." Backed by the Wailers and Rita Marley, it's a pleasant-sounding, if slightly inspired, imitation. Other songs, hardly less well crafted, dip into the well of Denver's recent personal challenges. "Time is a nonstop string of lovingly composed and sincerely sung songs with stirring melodies, even as it risks being corny.