Starting Strength (2nd Edition), by Mark Rippetoe & Lon Kilgore

This is an excellent and credible introduction to high quality barbell training.   The authors explain why weight machines are a poor choice (in brief, because they isolate muscles whose use in real life is not in isolation). They explain a core set of weight training exercises in great detail, particularly the squat, chest press, and dead lift, along with ancillary exercises (such as pull ups and chin ups).

Unfortunately for me though, I don't expect to get much practical benefit from this at the gym.   I'm not very adapt at proprioception nor am I a visual learner of physical topics, so in spite of the detailed explanations and great photos and diagrams, I'd be uncomfortable doing many of the exercises (the dead lift for example) without coaching.   Meanwhile, the authors imply one ought be cynical about the quality of coaching available at most gyms.   So what to do:  give a prospective weight trainer a copy of the book and see if that helps?