Listened to the latest episode of the Productivity Show, and they were talking all about how to really make use of the books you read. They break down the process into two steps, with slightly different approaches.
But both versions have the hosts capturing what they read with notes while they're reading the book. Then, they'll set reminders for themselves 3 days out, 3 weeks out, 3 months, etc. to review that book.
I feel like this could be really helpful for guitarists. If I'm learning a new riff, I never feel like I can truly attack it until I've memorized much of it. With memorizing it, I can focus on technique and making the notes clean. It also gives my brain a break if I'm trying to read tab, and already know a bunch of the notes.
Check out the podcast and see if you can develop a version of their system for learning songs and more.