This article analyzes evidence from a manuscript ledger belonging to the London bookselling firm of John and James Rivington during the early 1750s. The ledger shows that the Rivingtons, at the center of the London book trade, frequently swapped or acquired books from other booksellers for retail sale in their shop. The price valuations in the ledger also reveal that the books traded between booksellers were valued at a much steeper discount off the retail prices than previous studies have found. This article concludes by suggesting that the wide range of booksellers in their inner circle and the steep discount of prices for those on the inside explains how the Rivingtons and others at the center of the London trade were able to maintain their monopoly and also why they underestimated the threat from booksellers outside their network. The swapping of books gives insight into the retail experience and shows booksellers stocking common books even before there was an established canon of English literature.