I may just be stating something that you already know, but slugging a compressor is when you introduce a "slug" of liquid refrigerant into the compressor itself. Since liquid is not compressible, it causes the compressor to lock up. If the compressor is locked, then the belt will usually either fly off or break. Sounds like that is what the book is talking about. Eventually the liquid will usually turn back into gas, and the compressor will return to proper operation, making it look like the problem was someplace else. An overfilled system is usually the cause of slugging, but I have seen cases where the air passages in the evap coil are so clogged with hair or leaves that the the hot liquid cannot completely boil off in the evap coil and so it returns as liquid back to the compressor.