I think it could be well said that the GTA is THE comprehensive volume on all things airgun. Sure there are many pro tuners out there who keep their wisdom and tricks close to the vest, but thankfully they eventually migrate elsewhere to peddle their wares. All of the pros who eventually settle into the GTA realize that the more good information which is put out here to help individuals do their own thing will eventually translate into more business. The more folks that have a positive experience will come back many times over as they have friends, who have friends...and likely only one or two out of five will have the desire to do their own thing; the rest are are going to need/want someone with the right skill-set to do the work for them. Pretty much a win-win situation all around!
However, if you still need a hard copy of "The Complete Airgun Encyclopedia and Tuning Book"; get over to Staples, pick up 5-6 cases of printer paper and a couple gallons of ink and have at it! LOL:)