GURPS Powers: Enhanced Senses is an interesting project. Technically, it looks at all the possibilities for perceiving the universe, and shows how to represent them in-game by re-packaging the existing abilities. In actuality, it mostly limits itself to what is biologically plausible, and leaves much of the truly fantastic to other products; this still covers a fantastic amount of ground.

Since this is a Powers book, it starts with a look at Sources that (with Foci—generally senses or a sense organ here) define a Power in GURPS. This ranges from ‘natural’ enhanced senses, to hypercognition (concentrating your brain to nothing but the information already coming in), to implants, to actual superpowers. I’m a bit leery of the 5% cost break allowed natural biological passive senses here; this is given for “technological countermeasures ranging from TL0 herbs to advanced nanotechnology”, but since Perception rolls (including opposed ones for hiding, etc.) are part of the game definition of how senses work, this makes me a bit uncomfortable. But it does meet the system definitions for getting a such a break, and it’s a pretty tiny one.

There is then a good discussion of different qualities of senses, from Vague, to Discriminatory, and Precise, and other terms that have already been in use in GURPS. It’s a very good discussion, but stops short of being great in two ways: First, I’m not entirely happy with how the hierarchy works out, especially when Basic splits into three separate paths. But this is caused by working inside the structure of advantages already given. Second, I find the discussion, and the following section of modifiers easy to mix up. The general description of what a Precise sense is is in the middle of page 7, the modifier to make something a Precise sense is near the bottom of page 8, and I usually find myself looking for the former when needing to reference the latter. I think it would have been much better to put all the information about a particular term, what it means, and the modifier used for it, all in one place. Also, I think a short ‘under the hood’ box, spelling out in one place the definition of each standard human sense, would help with thinking about how modifying them works (i.e., ‘Hearing is a Basic sense, with intermediate-range in a 360° arc’). Of course, there’s already a couple of boxed sections in here, which do not help with the sense of a jumbled presentation.

Along the way, there’s still more useful information, such as a treatment of senses that can deal damage (an electric eel is mostly sensing his environment through his electric field; the shock it delivers is an extra). Active Electroreception (eels again) gets a write up under Vibration Sense, Infravision gets split into near infrared (modern active IR equipment) and thermal infrared (poor resolution, but you see radiated body heat), and a couple more. There’s even an entire page of skill bonuses from various sense types.

And then we get to the bulk of the book. I count about 85 ability write ups categorized by what they sense: electromagnetic radiation, electricity and magnetism, acoustics and vibrations, and the ever-popular ‘miscellaneous’ (which goes far afield, from chi to gravitational waves). This is the worked-out part of the book after the first parts establish the tools to be used. Most of these these are counted as ‘supersenses’, not really possible, but tend to show up in fiction, with almost equal numbers of ‘sensor implants’ (electronic devices) and ‘enhanced senses’ (modeled after actual abilities seen in nature, plus some that are obvious how they’d work even if they haven’t been seen). It’s a very impressive list, and I doubt I’ll ever touch the vast majority of it. Those parts I do end up using will be very handy though, and the fact that they’re part of a larger set of possibilities makes it easier to understand their niche.

As a focused product, you are generally going to be interested or not, but GURPS players not wanting to worry about outre senses may still be interested in the extra crunch given to the existing hearing distances (giving their equivalent decibel levels as a way of generating modifiers at different ranges), and the table showing just how much light corresponds to the various darkness penalties. The crunch focus keeps its usefulness down for the non-GURPS player, but the extensive listing of biological and superscience abilities could be inspirational for anyone writing up aliens and the like.