Having read several books on the art of estimating over the years, I have found that most are good for a few tips that can help but for a newcomer to the rehab business can leave them on shaky ground. The difference between the cost for a specific repair / renovation if you have a crew or need to find someone on a first time basis can be significant. We have trades we use on jobs and know what they will charge which is often considerably less than what Joe Homeowner would pay for the same job . . . the trades know we will be using them again and again. The renovation shows on TV reinforce that. Some of the costs quoted shock even seasoned flippers as they are lower than even material are in many markets. But again, dedicated crews drive reno costs down.
If you can connect with a flipper in your area (quick out your local REIG) and ask to come along when they scope out a job, you will get more from one or two trips than from a dozen books. We have put together forms that allow us to scope out properties on a walk thru and be pretty close to the final cost. My wife and I do it separately and see what each of us may have overlooked. Need to be sure you include the "unknown budget" and never take the optimistic approach as it is better to have money left at the end than writing more and more checks that were unplanned for.
Again, if you can walk through an actual property and compare notes with someone that does it in your area (key factor), you will be way ahead of what a generic book can give you.