Whitesnake kicked off the North American leg of The Purple Tour in May 2015. Joining the band was new keyboardist Michele Luppi. At a show in California, they were joined onstage by Coverdale's former Deep Purple bandmate Glenn Hughes. In December, Whitesnake teamed up with Def Leppard for tour of the UK and Ireland. In Sheffield, Whitesnake were joined onstage by former guitarist Vivian Campbell (who has been a member of Def Leppard since 1992). In 2016, the band embarked on the Greatest Hits Tour, which saw them perform across Europe and the US. Before the tour, Coverdale revealed his plans to potentially retire in 2017, though he later recanted the statement. In August 2017, Whitesnake signed a new distribution deal for North America and Japan with Rhino Entertainment and Warner Music Group. Tentative plans to release a new album the following year were also announced. In October 2017, Whitesnake's self-titled album was reissued as a four-disc box set to commemorate its 30th anniversary. The band had planned a joint tour where they would have played the album in its entirety, but instead opted to take a break and focus on writing a new album. In December, a photography book chronicling The Purple Tour was released, followed by a live album in January. In 2018, Whitesnake toured the US with Foreigner on the Juke Box Heroes Tour, and released the box set "Unzipped", which featured various acoustic recordings from the band's career.