this book was a key stepping stone from being a support engineer on a product built on top of the bsd kernel, to becoming a developer on said product and launch

this book was a key stepping stone from being a support engineer on a product built on top of the bsd kernel, to becoming a developer on said product and launching a career as a software engineer with no formal college education whatsoever. OS internals were something I could touch and feel on a daily basis, and then I could read and comprehend the code that underpinned it all. Great stuff.