Knowledge of mechanics is a stepping stone to many types of skilled jobs.
Gears, cams, pulleys, rings and clips; they're all here in this book.  2nd Edition contains two new chapters: Pneumatics & Hydraulics and Mechanical Troubleshooting.  134 pages.

Easy to read. Great gift for son or grandson.  For kids and adults.
By Joe Jacobs, former maintenance technician for the U.S. Postal Service. 
Start With Mechanics
table of contents for Start With Mechanics book
About the Author
Written by Joe Jacobs, a former maintenance technician for the United States Postal Service.  Trained on electronics and mechanics, he has worked on everything from simple conveyors to the best industrial automation machinery.
table of contents
Chapter 5: Mounting Parts