The flagship line for Palladium Books is RIFTS. First published in 1990, and building upon all of the company's catalog to date, this game became the flagship due to one explicit purpose for putting on the shelves: to allow the users to put anything together at the table and run it in your campaign.
Yeah, well, um, yeah. About that.
Look, there's a hell of a lot to say about this game. I have a (dormant) blog all about that where you can read my opinions upon, and attempts to clean up, the mess Palladium publishes as their flagship game. I won't rehash it here, but instead summarize why I keep at it despite my dissatisfaction.
- The setting premise is very friendly to interpretation, despite the droning of fanboys at the official Palladium forums.
- The mess does mean some bitchwork for Game Masters, but that's manageable. However, doing it properly for the setting does mean telling the snowflakes to fuck off because this setting--at no point--is friendly to SJW insanity.
- The game cleverly associates subgenres with geographic locations, making it easy for new GMs to isolate material to just what he wants to use.
- The massive catalog of material is firmly in the Rule of Cool camp, exciting readers and firing imaginations, using iconic imagery and decades of comic tropes as shorthand to get the concepts across.
- If there is an old-school game that's still in print (and never been out of print) that's firmly Pulp and approachable (and not old-school D&D), this is it. The mess creates a liminality that drives Mech Pilots nuts, filtering out the worst right there, but you need to beware of Fandumb and thus set your expectations clear and concrete up front for best results. It's also easy to run it in a Superversive manner, for those so concerned.
I can play and run nothing but RIFTS for the rest of my days and still not exhaust what this game has to offer, and that's just what's published and used as-written. Once you get comfortable and begin tinkering in earnest, you can see why this game has its loyal fanbase- such that some don't even play other Palladium games, nevermind other tabletop RPGs (or even other media).
And just using the core post-apocalyptic North America subsetting, featuring the Coalition States, I've got material enough for years of campaigning. If not for my interests elsewhere, I'd be running my version of the Tolkeen vs. Coalition war right now. (Hint: States that exist in economic scarcity can't win against post-scarcity opposition.)
The line is up at the Bundle of Holding this week, so if you do e-books this is a good chance to get in cheap and easy. Otherwise, find a Half-Price Books or some used bookstore like it; chances are good that you'll find it used and in decent condition there. Failing that, buy it new from Amazon or direct from Palladium's store. Love it or hate it, you'll find something good there to make it worth the scratch to have it.