I re-read The World of Null-A, The Players of Null-A, and Null-A three, by A.E. van Vogt in preparation for reading johncwrights Null-A Continuum. Obviously, the first book in the series is the best, and nothing which follows can quite rise to its level. That said, I think the next best of the books is Wright's - van Vogt had a habit of tossing dozens of ideas into a page, and then only exploring a couple of them. Wright has much of the same galactic/universal scope of van Vogt, but he seems a bit more concerned with making sure that it ends up making sense upon reflection. His work basically treats Null-A Three the way that most sf fans treat Highlander 2 ("what movie?"), but this is not a fault - Three is by a long margin the least of the books. I would say that this is a case where Wright's work can bridge space to join van Vogt's (this makes sense if you've read the books, and if you haven't, then I think you've got some reading to go do). The right sequence to read these is World, Players, and Continuum. And when you're done, go read The Weapon Shops of Isher, and maybe a few more of van Vogt's brilliant works.