About one hour, but very much worth it, no matter if you’re into Rails or Ruby (in fact, the choice of coding framework or language is quite ancillary in this day and age anyway).
Summarised nicely in a quote from his 2005 talk on introducing Rails: “Look at all the things I’m not doing.” and very much in line with this “Less is more.” ethos (of which “The 4-Hour Workweek” is another contemporary example), AI allows us to create more by orders of magnitude with much less effort.