It took a few albums for Matthew Sweet to become a commercial success, but 1991's Girlfriend was a worthy star vehicle: Complicated but catchy, diverse but accessible as a whole, the album was one of that year's most satisfying breakthroughs. Since Girlfriend, Sweet's records have become less ambitious; 1993's criminally underrated Altered Beast and 1995's criminally underexposed 100% Fun consisted mostly of killer pop songs and sweetly morose ballads. The new Blue Sky On Mars is his least challenging record yet, consisting mostly of nice, sugary three-minute pop singles that instantly lodge themselves in your cranium. "Where You Get Love" is the worthy hit single here, but it's hard to imagine fans not appreciating the hummable "Back Into You" or "Come To California." As a whole, Blue Sky On Mars comes off as a bit toothless: It's hard to explain the drum-machine track that opens the plodding ballad "Until You Break," and most songs lack the quirks and thematic dark edges that pervade Girlfriend and Altered Beast. Still, Matthew Sweet is one of the best pop singers currently recording, and Blue Sky On Mars is a slight but worthy addition to his terrific catalog.