The Cuckoo's Egg by Clifford Stoll. It really crystallized how to approach problems by continually drilling down through the layers to find what's really going on.
I've been working in the IT industry for 20+ years. While I've focused on Systems / Network Administration, I've always enjoyed doing a bit of everything, including DevOps, Full Stack Development, UX Design and Hardware Repair / Troubleshooting.
Right now, I'm looking to get back to working on a team. I've been consulting for a bit and, while I enjoy the variety of the work, I find myself missing the camaraderie of being on team, working towards a common goal.