Tim Waterstone, the bookselling entrepreneur who founded the chain, will be non-executive chairman. He will work almost full-time to start with though may take a less hands-on role later on.
The deal will not initially include Mr Waterstone's Daisy & Tom children's shops. Management on both sides felt the due diligence process had already taken long enough and were reluctant to delay the deal any further. However, Daisy & Tom is expected to become part of the group at a later stage.
EMI is leading the joint venture, which also includes Advent International, the US venture capital group which is backing Mr Waterstone.
The completion of the deal could lead to around pounds 250m being returned to shareholders.