I assume it's the same thing as signal is for me: it's the thing with UX good enough to convince some of my friends to use it. They wouldn't use buggy xmpp, tox clients or things without many of the features like ricochet.
I like testing these tools with cryptonerd friends though.
I have done it fairly extensively for many years now. Generally, the book should be a light read, and the task fairly mundane. If the task is very simple, then "reading" this way might be more better than listening to an audiobook sitting down and doing nothing else. For more complicated tasks I am usually expecting to skip dozens of seconds of the audiobook now and again, so I either choose a book I don't mind reading poorly, or a podcast. For tasks that require reasonable amount of attention, I sometimes do lighthearted podcasts, but that comes with accepting slower work. Sort of half working, half passing time.
Books past a certain complexity, or ones you want to read well, or quickly, are best read the old way.
I'd say audiobooks are awesome for squeezing that extra use/fun out your time, but they have to be done in a smart way.
I like testing these tools with cryptonerd friends though.