Mike Luckwell acquired the magazine for a token price from Jon Moulton's Better Capital, which rescued it from administration in 2010.
Better Capital has decided to exit the business after investing £23 million, including the £13m purchase price.
Mr Luckwell believes the title can help take "crumbs from Saga's table" by concentrating on the over-50s market and exploiting financial services opportunities.
Mr Luckwell is thought to have amassed a personal fortune of more than £100m after a series of profitable investments in the likes of Carlton Communications and advertiser WPP.
In 2005 he made £33m from his stake in children's TV company HIT Entertainment, which owned the copyright to programmes such as Bob the Builder. Reader's Digest is sent to nearly half a million subscribers.