The material invites you to reconsider your core beliefs, but gently. Can change your life, if you allow it to do so. Tolle has surprising insight into Christianity and Buddhism, and reveals their deeper, common truths, and does so without academic arguement.
Don't bother learning *the tricks of the trade* -- learn the trade. In this case, the trade is playing music on a guitar, and its not just a series of tricks. With this sort of attitude and say, ten years, you'll have 10 years experience being a first-year wannabe. Music is made from Melody, Harmony, Rhythm... so, do the work: learn Music, not tricks about music.