The short version of my advice to them would be: don’t publish a digital edition of the whole multi-volume set. Instead, distill out an app that’s highly focused on handling some of the in-the-kitchen reference chores and computational wonkery that any modernist chef has to perform.
And the same goes for magazines. Yes, there’s step 1: a digital version of your magazine so that people (like me) who are trying to switch to e-versions can do so. But when it goes beyond that, don’t try to do everything in one app. Think about how your brand can translate into an e-version that is using the technology to its fullest rather than just duplicating paper.