Diving straight in with an analysis of the key components of the classic dungeon trap (they are sprung by predetermined events, they usually take the characters unawares and they hurt!), they are then divided into two main categories - mechanical and magical. However, while that distinction is important to the trap builder, as far as its intended victims are concerned it is far more vital to know how easy it is to spot (before it is sprung, of course) and if it can be disarmed.
Moving straight on to the rules for trap detection, the greater the success of a character's Scrutiny roll the more he knows about how to avoid or even disarm the trap. If the roll is only just made, he knows there's something wrong here... up to being able, with a spectactular success making it obvious how the trap is triggered, how it works and how (if?) it can be rendered safe. You do have to be actively looking for traps, though - they are rarely apparent to those wandering around without paying attention to the matter. Disarming traps is again based on the original difficulty of the trap, with either Thievery skill - for mechanical traps - or Arcanum - for magical ones - being used to roll against the trap difficulty.
Looking to the other side, there is next a discussion of what is needed to create a trap, be it mechanical or magical. Naturally a character wishing to build a trap will need relevant skills, and if it is a magical one that is required a specific arcane ritual aimed at trap-building is needed - just because you can cast fireballs, say, does not mean that you can build a fireball trap without devising a separate spell for that purpose. Finally, a series of example traps both magical and mundane is given.
It is good to see a detailed and logical analysis of what traps are all about, and how they operate within this particular ruleset. It should enable GMs to set traps in a consistent manner - and characters might wish to either make a study of them or even protect a stronghold or base.