Within the past five years, Barnes & Noble has lost more than $1 billion in market value. Amazon holds nearly half of new book sales, a report by audience research Codex Group said last year, while Walmart has about 4.2 percent of the market In search of a turnaround, Barnes & Noble said last year it was exploring a sale after having received "expressions of interest" from "multiple parties," including its chairman, Leonard Riggio, who founded the company in 1965. Riggio has entered into a voting agreement in support of the transaction, the company said Friday.