Admittedly, this album is, superficially speaking, differently sounding than the rest of their (later) material. But make no mistake: this album adheres to the DM aesthetic in many ways. It forms its own unique niche in the history of this band. And just like all of DM's other classic albums of the mid to late '80s and early '90s, it's superbly inventive, crafted, and produced electronic pop that strives to appeal to the highest common denominator of the record buying public. As one reviewer wrote about this long ago: "DM introduce literacy into bubblegum".
Compared to DM's later efforts, the lyrical content and melodies here are pretty fluffy. But the underlying ideas here are great: Daniel Miller and the band went into the studio with the idea of creating an electronic pop album with a highly minimal Kraftwerkian aesthetic, but also with a poppy sweetness which had never been married to this style of music before. Today the album sounds equally dated and relevant; in other words, great art that not only evokes the time in which it was made but also occupies its own irreplacable spot in this history of this band and perhaps in that of music as a whole.
Some may call me crazy, but I love this album for its classic electronic minimalism a la Kraftwerk, its almost total lack of pretense, and also just for the fact that its a blast to listen to. But I would not recommend this as an introduction to the band for a first time listener as it, while certainly being very good, is neither their best nor a broad overview of Depeche Mode; instead purchase "The Singles 81-85" (which has the three singles released concurrently with "Speak & Spell"), become further acquainted with the band and only then get this album and see it in the context of their later work (and that of other innovative electronic acts of the time like Kraftwerk).