The multi-channel publication, which is produced in a concertina format with hand drawn illustrations, will look at all areas of print and digital marketing, with the first issue tackling "generational" marketing after the results of a recent YouGov poll showed marketing was not successfully reaching audiences outside the core 25-54 working age group.
In the Flow, which has been sent to 1,000 senior marketers, is also being published in digital format at http://intheflow.therivergroup.co.uk/
Contributors to the first edition include Age UK managing director Duncan Lewis, Honda marketing director Martin Moll, marketing expert Laurie Young, footballer and youth audience publisher Rio Ferdinand and River chief executive Dr Nicola Murphy.
River's business development director Adrian Odds said the new publication was designed to highlight the importance of content strategy in marketing. "We want to demonstrate innovation in marketing with print solutions as well as in digital," he added.
"It shouldn't be assumed that one channel is right for a given audience just because of their age. Choice of channel should be based on what customers want.
Odds said: "Print has the ability to reach across all generations - it speaks a language that digital doesn't. That doesn't make it right or wrong, it's just different and together they are a very powerful tool."
