This album of powerful guitar driven music marked John Lydon's return in the 1990s. Lydon is assisted by John McGeoch, Alan Dias and Curt Bisquera. Acid Drops is a scorching slab of heavy metal, Lucks Up is similar, a farewell song to a drug abuser. The thrash metal vibe continues on Cruel and Covered, whilst Unfairground and Love Hope have a more eclectic mix that includes harmonica and psychedelic twists and turns. Lydon's piercing voice rides the sonic wave to impressive effect. Emperor is a frenzied throwback to his punk roots, Good Things is a type of retro electro with a funky rhythmic undertone and Think Tank has a catchy tune and almost singalong chorus. That What Is Not is a strong album of neo heavy metal, exploring various avenues of the genre. It also contains some great melodic songs with intelligent lyrics and Lydon's trademark caustic observations. This work is as good as anything he came up with in the previous two decades, including the Metal Box set and his work with Sex Pistols.