Buying shares, commodities, etc., long (i.e. without having sold them) or selling them short (i.e. without having bought them) for one's own account. Making a book is therefore a speculative activity in which market makers and dealers, but not brokers, indulge. A dealer will often have a complicated book, with many transactions open (see open position). Whether the overall position is long or short will depend on the dealer's view of the market.
Subjects: Financial Institutions and Services.