International Book Center (IBC) is one of the bigger book stores in Phnom Penh, they supply both books in various languages and office stationery. In addition to books and stationery they also sell sporting goods, holiday decorations and souvenirs.
You can also find other branches at IBC-International Book Center (Sihanouk), IBC-International Book Center (Kampuchea Krom), IBC-International Book Center (Mao Tse Toung).