The fact that book and mail bombs have reached a stage of easy construction and great sophistication means that all packages, particularly those containing books or those that are not expected, must be treated as if they contain bombs. It doesn't take a doctorate at Harvard to put a killer bomb together. It is obviously not practical to have bomb disposal people open each and every package or book that comes into an office or home. Understanding how these types of bombs work, and what they look like, can aid possible recipients of letter and package bombs in identifying suspect materials. Package bombs, including book bombs, are often triggered by electrical systems.
Most letter bombs use a mechanical detonation system rather than an electrical one.
The pressure of the envelope around the device keeps it from detonating. And almost never is that type of technology or procedure in place to protect people from handling any package or letter bombs that are sent to the homes of employees or managers. There are procedures and checklists that can fill at least some of these gaps. As explained before, they should make people a little safer, whether at home or in the office. The first rule is to never open any letter or package until you have inspected it thoroughly.