Buckle up! This is GURPS Time Travel (the revised second edition from 1995). Before we dig in though, let us pause and appreciate that magnificent cover painting by John Zeleznik. Triceratops vs. Future Man. I would hang that next to Charles Knight’s Triceratops vs. T-Rex, I kid you not.

Moving on. GURPS Time Travel is a masterpiece. There are far too many GURPS books for me to have any idea which is The Best, but this one should certainly be in contention. It is the definitive RPG book on time travel to date, to my knowledge, for ANY system. For real, its pretty light on GURPS-centric rules, so you can use this for reference for any game that dips into the timestream.

In fact, it is an excellent primer on time travel in general. There’s plenty of discussion of both scientific thought on the matter (outdated now, but still handy) and much chin-stroking over the various strains of fictional time travel. This mechanical pondering of time travel takes up about half the book and covers pretty much all the time travel bases I am willing to consider (I admittedly have a low tolerance for time travel stories!). This forms a bedrock upon with Jackson and science fiction author John M. Ford build a number of campaign frames, both large (Time Corps!) and small (time jumping via drugs!). A lengthy section on parallel earths and all the messes time travel can make rounds things out.

I don’t really know how to convey how wildly out there the book is. The casual discussion of paradoxes and other theoretical quirks of time travel is both boggling, deeply entertaining and omnipresent. It seems intentionally complex, like the book is trying to make you wave your arms in the air in exasperation — and there is a wily fun in that pseudo-frustration. Without a doubt, this book, sitting at the crossroads of all worlds, times and possibilities, is the true and secret heart of GURPS.