Apart from Marx himself, so far the most useful book I have read about Marx and money is:
Marx on Money by Suzanne De Brunhoff (1973 French, 1976 English translation). The link goes to a searchable pdf which can be downloaded without sign in. A review of part one of this book has now been published on this site, here
I’ll just setup this page now as a placeholder since we need a thread to post links about Marx on money. This page is being updated as new references come to hand.
updates (see comments for discussion about these):
Introduction to Money and Totality: Marx’s Logic in Capital by Fred Moseley. Provides a useful overview and the authors conclusion of the outcomes of the papers presented to the 2003 Marx’s Theory of Money conference.
Marx’s Explanation of Money’s Functions: Overturning the Quantity Theory by Martha Campbell. Also see the comments about this paper in the third column at Papers. Now summarised and discussed on a separate thread on this site: Martha Campbell debunks the quantity theory of money
Marx’s Theory of Money in Historical Perspective by Duncan Foley.
Money in the Circulation of Capital by Martha Campbell. An excellent account of the importance of the Volume II material on turnover.
The Culmination of Capital: Essays on Volume III of Marx’s ‘Capital’ (v. 3)