Claiming to be Europe's largest virtual and second-hand bookstore, the tie-up with JustBooks extend's BOL's reach to include more than 1.4 million out-of-print and rare titles.
Books director Robert Nichols explained that the move comes as a natural extension for BOL, by giving its customers a wider range of books.
"In the UK, there's something like one million titles out of print. We want to be able to offer an integrated solution by using JustBooks' UK database as our own," he said.
Although BOL is currently relying on JustBooks' network of 1,200 UK dealers, it intends to develop its own rare and out-of-print service within the next six months.
The facility has been added just weeks after BOL announced it would be selling audio books, through a partnership with digital audio firm Didio. The next step for the e-tailer will be the introduction of US titles in the UK through a partnership with a US supplier.