I think they are well worth the money if acquired in a timely fashion. Had I invested in some earlier I could have easily recovered the cost of the books by not loosing valuable collector rifles through ignorance in one way or another. Knowledge is far more than money when lack of information leads to embarassing memories of establishing a learning curve the hard way. I would rather have the knowledge than wincing with visions of mongolian cluster flocks.
Before & after.
Equally important is finding a forum like this with knowlegable members who are willing to tutor others and exchange informaton to save their hides.