When it dropped in 1999, the third album from the Backstreet Boys broke just about every record you could think of, besting Garth Brooks’ previous stats for single-week sales and ultimately becoming the year’s best-selling album. Back then, you couldn’t leave the house without hearing the silky harmonies of the Orlando, Florida, five-piece. Narratively, “I Want It That Way” may have been a bit of a head-scratcher, but its earworm chorus embedded itself into the fabric of pop history, while the Latin-tinged lushness of “Show Me the Meaning of Being Lonely” soundtracked the collective ache of millions of teenage yearners. A quarter of a century later, Millennium still stands as one of the best-selling albums of all time. Here the boys (er, men?) don their vintage white getups to recreate the cover photo for the anniversary edition, which features remastered versions of the original tracklist, a handful of demos and live recordings, and one new single, “Hey.”