I recently read The CNC Cookbook by E. Hess and thought I’d mention it here. The book contains most of the information needed to get started designing and building a small CNC machine, and is pretty easy to follow.
The book covers each component of a CNC system, detailing the hardware and software involved. The making of a homebrew machine and conversions of existing benchtop machines are shown in detail. Other topics discussed include designing and building the controller box, selecting the proper stepper or servo motors, and power supplies. The Mach3 control program, the primary piece of software used by homebrew CNC systems, is also covered in detail.
The book is not a set of plans for any particular controller or machine, but it goes a long way in bringing you up to speed on all that’s involved in building one. It’s not an instruction manual on machining, setups or other practical matters. You can find most information covered in this book by searching multiple sites on the internet, but the book brings everything together into one place and allows you to focus your efforts on specifics. It’s a good read for anyone starting out on their first CNC conversion or build project.