Though this was designed as a big crossover, it's really just the fourth of volume of Rai tied together with miniseries that depict the past of Rai and the past and future of other Valiant heroes. There's almost no actual crossover between the three threads of story. Nonetheless, this volume is well worth picking up. 
 The core 4001 AD comic, which continues the story of Rai is the weakest. It's a perfectly OK story, but not too surprising. 
 The Beyond Japan one-offs are next up. They nicely detail the futures of Valiant heroes in interesting and unexpected ways. They aren't just the stories of legacy heroes who took the costumes. The new heroine, War Mother, is the weakest, but I'm interested in learning more. 
 The Rai comic, which depicts the history of Rai, is the best, because there's lots of great background here, both for the hero and the series.