It’s safe to say that in addition to being one of modern music’s most enigmatic bands, Sigur Ros has also become one of its more divisive. To some, they make the most beautiful music imaginable, goosebump-inducing work of the highest order. To others, they have increasingly become a band making pretty but empty music, more interested in bombast than in real depth. While there are those who would happily drift off to dreamland listening to the band, there are others who say this stuff just puts them to sleep.

From the slow build up of opening track “Eg Anda,” with its whispered choir vocals and quietly insistent chiming melody, it is obvious that Valtari will not seriously sway the band’s critics or their fans in any direction. At the same time, the album is not exactly business as usual for Sigur Ros. Where their previous album took them in an unexpectedly quirky pop direction (lead single “Gobbledigook” sounded oddly like Animal Collective) Valtari is a return to the more textured work of their untitled third album (the one with the brackets for a title, as most people know it).

Valtari shares that album’s feel in that it is supposed to be consumed as one complete work rather than skipped through for your favorite tracks. As such it represents a kind of return to Sigur Ros’ roots, with a slight but obvious electronic influence from the Riceboy Sleeps album (a collaboration between lead singer Jonsi and his long-term partner Alex Somers, who also co-produces this album).

The opening three tracks on the album probably represent the best 20 minutes of music the band has produced since the brackets album (as I will now refer to it). The aforementioned opener is wholly representative of what to expect from Valtari, with crackling textures and Jonsi’s unmistakable voice. On “Ekki Mukk,” that voice is used to extraordinary effect. Sigur Ros has always been smart enough to use Jonsi’s voice as an instrument and texture in its own right rather than just as conventional vocals, and “Ekki Mukk” feels like one of those timeless songs the band is capable of creating, completely self-contained, both subtly complex and almost nursery-rhyme simple.

By the time “Varúð” reaches its explosive climax, which feels both cathartic and glorious after the album’s tension build-up, Valtari is beginning to sound like the best Sigur Ros album of the past decade. “Rembihnútur” follows this opening with a typically lovely comedown, complete with a string section straight out of the band’s best work and crunchy drums in the background.

While the majority of that opening half plays to the band’s strengths, certainly managing more depth than Sigur Ros achieved on the last album, the remainder of Valtari does unfortunately expose the band’s long developing weaknesses. “Dauðalogn” is pretty enough but sounds thinner than everything that has preceded it. That then blends straight into “Varðeldur,” which sounds like a single idea stretched out to six minutes.

Where Sigur Ros has shown intuitive use of repetition and loops in their best work, here it just sounds a little simplistic and lacking in direction. Indeed, the last three tracks on the album sound like works in progress. Jonsi has admitted that some of these tracks are reworkings of much older songs, and the final twenty minutes of the album do have the feel of music that is unfinished. It is never anything less than pretty, but it does not move in the same way as their best work.

The result is an album that is good rather than great, immensely listenable but not really comparable to career highlight Ágætis Byrjun. And while that should be enough to satisfy fans, the fact that it feels inessential as a whole remains a frustration on this occasion, just because there is some truly glorious music on Valtari, music with the kind of sky-scraping, heaven-invoking beauty that only this band seems capable of. Valtari is about half of a great album, and half a merely pleasant one.

For more details on the album and forthcoming tour, including a Los Angeles date in August, visit Sigur Ros’ website.