The group's self-titled debut was compiled by the bandmates' families, using live sessions and studio recordings.
The album has toppled Elo's "All Over The World, The Very Best Of", reported Guardian.
"I think they'd be absolutely thrilled," Viola Beach star River Reeves' brother Finn said.
"I can see the smiles on their faces. They made this happen. They did the hard work."
The four-piece and manager Craig Tarry died when their car plunged into a canal in Sweden in February.
