Musically, Cassie is an R&B and pop album with hip hop influences, containing "looming synthesizer patterns" and "ice-cream-truck melod[ies] to give it a slightly twisted and threatening edge", as well as "flippant playfulness".

[9][11] She finished high school in 2004, and instead of going to college like her peers, Cassie moved to New York City, where she returned to modeling and classes at the Broadway Dance Center.

[9] They were introduced by Diddy's makeup artist, who had worked with her on a modeling photoshoot, and in February 2005, the two wrote a duet called "Kiss Me", as a result of Cassie being asked by her mother to record a song as a birthday gift.

[9][11][13] Mottola offered Cassie a management deal, and Leslie signed her to NextSelection Lifestyle Group, his music-media company founded with online marketing partner Rasheed Richmond.

That same year, they set up a MySpace page, where they uploaded the song which soon went viral and became a club hit in Germany, creating a label bidding frenzy.

"[16] Cassie also mentioned "Not with You" was one of her favorite songs, "It's slow, it's simple, and you get to really hear me as opposed to all the synthesizers and everything in the background," and compared the second single, "Long Way 2 Go", to Vanity 6's vibe.

[17] Cassie made television appearances on MTV's Total Request Live and BET's 106 & Park to support the album on its release week.

[25][26] The official music video for the track featured Cassie in a solo dance rehearsal, which drew comparisons to Janet Jackson's "The Pleasure Principle" visuals from 1987.

Cassie, a fan of Jackson, explained the concept came from Mottola and Diddy who suggested the idea after watching her rehearsal videos dancing alone in front of the mirror.

"[5] Rob Sheffield of Rolling Stone praised Leslie's production, "a master of the minimal electro hook, whether he's going for an R&B ballad ("Kiss Me") or hip-hop ("Long Way 2 Go")," while Cassie "shines with her understated cool", highlighting "What Do U Want" for mashing "bhangra with the Go-Go's [...] But the whole album coasts on the hypnotic groove of "Me and U".

"[33] Writing for the Los Angeles Times, Casey Dolan considered that Cassie "has fashioned an album that slots easily into the new hybrid stream of R&B with nods toward hip-hop and pop.

Her distinguishing vocal delivery is soft and languid, unlike almost every other singer out there who shouts you into submission," continuing that it "deftly flirts with adult themes but in a youthful way".

[6] Kelefa Sanneh of The New York Times said that the album "mastered R&B-lite songs over space-age beats", noting the track "Ditto" as a standout.

"[8] Blender's Dorian Lynskey wrote, "Even the 35-minute running time indicates a rare self-control that makes this the most consistently arresting R&B debut since Kelis's.

"[34] Clover Hope from Billboard stated the album "offers sexy, laid-back tunes, dainty ballads and midtempo dance jams" and its "whispery piano runs and simple basslines create a fresh listening experience".

[42] "Cassie's is the kind of voice that demands your attention without caring whether or not it gets it," Noisey's Emma Garland explained, "It's spacious, seductive and borderline melancholy, which is why her material has been heavily sampled and remixed by an endless list of artists and producers.

mysteries [...] it’s a great, influential record, like the LP Aaliyah could’ve gone on to make in terms of the production; it’s got that 'mad-slow techno' vibe that Weatherall talked about in Jockey Slut all those years ago when discussing 'acid r&b.'

It's well documented how her icy delivery and the cold production made a big impression on the Tri Angle Records crew as well as others like Four Tet and The xx etc."

Described as a "seductive debut" and "late-night classic of chilly electro-soul", it was officially licensed and cut at Abbey Road Studios, continuing, "The dark, hypnotic high ends coupled with Cassie's ice-queen delivery made this stand out from the tired crowd of mainstream r'n'b at the time.

[65] The Quietus listed it as sixth among the top 100 of reissues, compilations, DJ mixes, live albums, and other releases of 2015, "with its ultra crisp, economical production, giant shiny hooks and ultra-satisfying bass, with tracks evenly divided between clubby R&B and straight up pop.

"[66] In 2021, Rolling Stone named Cassie one of the greatest "one-album wonders" in music history, describing it as "the most brilliantly minimalist R&B album of its era.