LONDON (Reuters) - Amy Winehouses posthumous new album Lioness: Hidden Treasures hits stores on Monday, but the one fan who will find it hardest to listen is her father. Mitch Winehouse, who has set up a charity in his daughters name after she died in July aged 27, heard the collection of 12 songs recorded from as early as 2002, a year before the release of her debut album Frank. But he said the experience had been difficult, with the memories of the late chart topper still raw. We were finding it difficult to listen to Amys music, but we had to listen to it because if it wasnt up to scratch we wouldnt have allowed it to go out, Mitch told Reuters in a recent interview. We werent pleasantly surprised. We were stunned at how wonderful the album is. (But) at the moment I cant listen to it. In the years to come I will be able to and people have to make their own minds up. Early reviews of the album, released on Universal Musics Island Records label, have been mixed. It was clearly a bit of struggle to cobble together the material for this album, said Alexis Petridis of the Guardian newspaper in a three-out-of-five star rating. Helen Brown of the Telegraph wrote: The random scrappiness of this collection of alternative takes, covers and sketchy new material is made poignant by the context in which it has been released. And ... it lays bare what made her both such a unique and such a troubled artist. Winehouse released just two albums in her brief career, with 2006s Back to Black, featuring hits Rehab and Love is a Losing Game, confirming her as a major talent and earning five Grammy Awards. The artist famous for her beehive hairstyle and rich, soulful singing voice, struggled with alcohol and drug addiction, had a troubled marriage and was often in the headlines for the wrong reasons. When Winehouse died at her north London home there were high alcohol levels in her blood, and her last filmed performance was in Serbia in June when the singer was jeered by the crowd as she struggled to perform songs and stay upright. Lioness: Hidden Treasures features 12 songs and demos chosen by producers Mark Ronson and Salaam Remi, who both worked with Winehouse when she was alive. They include Body & Soul, her final studio recording and a duet with Tony Bennett which also appeared on his recent album. The song has been nominated for a Grammy in the best pop duo/group performance category. Singled out for praise by critics were the reggae-infused cover of Our Day Will Come and Halftime, while the two tracks from recording sessions for the third album that never materialised Between The Cheats and Like Smoke featuring rapper Nas, merely underlined what might have been.