Since Diane Warren was the most successful songwriter of the '90s, it is surprising that nobody devoted an entire album to her songs until Johnny Mathis did in 1998.

Of course, Warren's renown was slow to build, since she achieved her success the old-fashioned way, by writing and pitching her songs, but not actually recording them herself.

Still, by 1996, when Warren's songs occupied the top of the charts for ten weeks (six weeks with Celine Dion's recording of "Because You Loved Me" and the first four weeks of an 11-week run by Toni Braxton's "Un-Break My Heart"), even casual pop music fans could tell you who she was.

She is the queen of the contemporary romantic ballad, whether performed by pop, rock, country, or R&B performers (indeed, her songs have proven readily adaptable to all genres).

They are characterized by slow or loping tempos, strong hooks, and nakedly emotional lyrics, pop songwriting craftsmanship at its best (or, depending on your point of view, its most contrived).

Could any material be better suited to Johnny Mathis, a singer who has devoted his career to love songs, feelingly rendering them in his immediately identifiable tremulous tenor? Not surprisingly, Mathis showed tremendous affinity for Warren's songs, choosing ten of them from among the songwriter's many hits, from 1989's "All I Want Is Forever" (originally taken into the R&B Top Ten by James "J.T." Taylor and Regina Belle) to "Un-Break My Heart." Since Warren has managed to place her songs well with exceptional singers who did them justice, Mathis didn't really improve on any of the original recordings.

Rather, in the manner of the old days of non-writing singers and non-singing songwriters, he rendered the songs in his familiar style for his fans.

Of course, we now live in a time when songs tend to be identified with specific recordings by specific singers, which diminishes the impact of Mathis' achievement.

Though the album works as a songbook, one wonders why Mathis didn't commission ten new songs from Warren, giving him the chance of scoring a hit.

Still, this is a distinguished step on Diane Warren's path to full recognition of her talents, and a typically high-quality effort from Mathis as well.