It's one of only five albums released under the Aphex Twin name over 20 years by maverick electronic music genius Richard D. James. He records under at least 15 other different monikers, in a dazzling variety of styles from breakbeat to techno, and including - in the off-kilter space-funk of and the disturbed industrial metal/breakbeat hardcore of - two of the more unlikely hit singles of the 1990s. But is Aphex at his most other-worldly.

By turns haunting, soothing, insistent, lush and disturbing, the album is pared down to a minimal number of sounds, with timbre and atmosphere taking precedence over melody and rhythm. It's based on endless, slightly morphing mutations, washes of synth, bleeps and skitters, half-decoded signals from the other side. Listen to it a few times and it will find its way inside your head and stay there - every sudden, subtle variation in tone, texture and mood.

At times it's ambient in the original sense - it surrounds you, envelops you, exists without you knowing it's there - but this is far too haunting and intense to be background music. At others it's more radically minimal than ambient; its overwhelming sense of sonic absence demands attention.

Except for one, , the compositions on the album - "songs" don't really cut it as a description for these non-linear, layered slices of sonic strangeness - don't have titles; instead, they have symbols in the liner notes from which fans have given them names such as , and . Squarely in the Brian Eno/Philip Glass/Stockhausen tradition, there are 25 compositions, lasting more than 21/2 hours in total. Specifically, sounds like a sliver of an alien voice reaching the listener from afar, while is like radio interference containing a coded message from another galaxy. comes across as a slowly oscillating alien frequency, the science fiction theme to a new half-algae, half-robot race, while the album ends with the perturbed sci-fi of . James, who as a teenager pulled electronic instruments apart and put them back together again so they could better channel the frequencies he was picking up, generally comes across as orbiting a different planet from the rest of us.

His space-cadet persona is partly cultivated: his trademark perma-grin, living in a disused bank, driving a tank. He also once claimed to write his songs by lucid dreaming. But on , it really does sound as if he's wired up to the heavens and is just transcribing what he hears.