Hundreds of jobs are at risk after The Book People went into administration.
PwC has been appointed administrator of the company - which has a large delivery warehouse in Bangor and head office in Godalming, Surrey.
The company employs nearly 400 staff.
It was founded in 1988 and has become a long-established retailer specialising in selling children’s books and collections at competitive prices.
The appointment of administrators is a result of the difficult trading environment that the business has been experiencing, combined with increasing working capital pressures.
Toby Underwood, restructuring partner for PwC, said: "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.
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"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 business is primarily an online retailer, with over 76% of sales through its online platform.
Other sales are made by self-employed distributors who deliver mobile book school fairs and buses, and pop up stores in workplaces.
The business has an annual turnover in excess of £50 million, employs 393 staff and sells over 17 million children’s books each year.