||While open access publishing for journals is well established, open access monograph publishing is taking longer to gain momentum. This is in large part due to the financial challenges involved in publishing monographs. Publishers are concerned that the availability of a free open access edition will cannibalise print sales and therefore the publisher’s ability to recoup the costs involved in producing a book i.e. peer review, editing, typesetting, technological infrastructure, sales, marketing and staff. But is that really the case? Or does the availability of the open access version mean wider access to the book, all round the world and to new audiences, and in some cases increased print sales as a result of the greater visibility? This article will look at some statistics from the OAPEN-UK / Jisc project that has been investigating open access monograph publishing during the last five years. As part of its research, the project ran a pilot comparing open access monograph download figures with print sales of comparable books to assess what the effect on print sales actually is. It will also review the Knowledge Unlatched pilot, which made 28 books by a range of publishers available as open access, with some interesting results. The outcome of these pilots will be compared with UCL Press’s own experience since launching as the UK’s first fully open access university press in June 2015, along with some examples from other open access publishers.