The Book People has gone into administration just one week before Christmas.
The company, which was founded in Surrey in 1988, employs nearly 400 staff across the UK with 229 based in Bangor.
Over the years it has become a long-established retailer specialising in selling children's books and collections and also sells gifts, toys and stationery online and via a catalogue.
Customers have been assured that the firm's intention is to "fulfil and deliver" all orders that have been received and accepted.
PricewaterhouseCoopers (PwC) has been named as the administrator, as the company searches for a buyer.
PwC announced that there are no plans to make any of the 393 members of staff redundant and explained that the business will continue to trade.
Toby Underwood, restructuring partner for PwC, told the Daily Post: "I can confirm that the business continues to trade and at this point in time no redundancies are currently envisaged whilst we rapidly explore a sale of the business.
"The intention is to fulfil and deliver all customer orders received and accepted.
"I appreciate the obvious concerns that staff in particular will have as we move towards Christmas.
"Whilst the administrators have funding to meet the payroll for December, the longer-term prospects for the business, staff, customers and suppliers will clearly be dependent upon whether a sale can be secured."
The company has an annual turnover of £50 million and sells more than 17 million children's books a year.