Wu-Tang Forever, the highly anticipated double album by Wu-Tang Clan, will enter Billboard at No. 1 next week after selling 612,000 copies. That's a phenomenal figure, but an increasingly routine one in rap.

It's eclipsed by two recent posthumous releases: Tupac Shakur's Don Killuminati: The 7 Day Theory sold 664,000 copies; Notorious B.I.G.'s Life After Death sold 690,000 copies. In the past 18 months, only one other release, Metallica's single-disc Load, exceeded first-week sales of 600,000, according to SoundScan.

``I guess rap's still popular,'' quips Geoff Mayfield, Billboard director of charts. ``Conventional wisdom says a double album is a harder sale, but if an act's really popular, fans will pay the extra bucks.''