5 Books?
1) HERO 5Ed
2) Deadlands
3) Arcana Evolved
4) Traveller
5) Space: 1889
AE would be my 1 book D&D substitute. Deadlands & Traveller stand up on their own, Space: 1889 is simply a very rich setting, easily as imaginative as RIFTS, but with better mechanics. Any other genre of gaming, I'd run with HERO.
Not that I couldn't run any of those in HERO (because I have), but that's beside the point.