This is a very helpful introductory book for someone who has little experience in the oil field. I wish I would have read this prior to arriving on the job as it helps break down each facet of a typical drilling operation. Those that say it is too simplistic just had too much experience or knowledge on how the operation works going in. This is perfect for somebody who doesn't know a BHA from a Kelly and everything in between. Can't recommend this enough for someone going into their first job on an oil rig. I am an MWD just starting out and still found much of this information useful.Only recommendation I can think of would be for someone to write a similar manual for brand new MWDs with little previous experience!