Humble Bundle offers various e-book bundles for a limited period of time very cheaply, with part of the proceeds going to a charity. For the next 17 days or so, you can get bundles of Wiley "for Dummies" books related to guitar.
https://www.humblebundle.com/books/g...es-wiley-books
For example, 18-book bundle for $18:
Guitar Amps & Effects for Dumies
Music Composition for Dummies
Blues Guitar for Dummies
GarageBand for Dummies
Logic Pro for Dummies
Home Recording for Dummies
Music Business for Dummies
Bass Guitar Exercises for Dummies
Rock Guitar for Dummies
Classical Guitar for Dummies
Guitar Theory for Dummies
Guitar Rhythm and Technique for Dummies
Guitar Exercises for Dummies
Bass Guitar for Dummies
Guitar Songs and Styles for Dummies
Getting Started Playing Guitar for Dummies
Guitar Chords for Dummies
Guitar for Dummies
The last four books are available in a $1 bundle. The books from Bass Guitar Exercises on down are a $10 bundle.
Not sure if any of these are stellar (I've only looked at them at the library), but you might be interested. I have no connection to this -- I've bought a few tech book bundles from them in the past.