for me :

the time line
the text about behavior in the ol' street sam catalog
a novel or two (of the player isn't shittin' on readin') (maybe trilogy of power...)

maybe look for "ronin' movie

any other idea ?

Quite a few people praised the Sprawl Survival Guide as a must, especially the chapter "Life on the Run", though "Living in the Sixties" can be a good idea as well.

The BBB, specifically any sections of relevance to their character (ie. Magic, Matrix, Rigging/Vehicle Combat) and at least skimming over the other sections.
Sourcebooks of relevance (MitS, Rigger 3, Matrix,...) : cover to cover.

A complete, overall timeline, amalgamating all the timelines printed so far, even from the out of print sourcebooks like the London book. as well as a handy reference, it allows Gms playing outside the current time frame (like us - we just don't manage to keep up with the books! We're still in 2060!) get to set their players up to be involved in the big stuff. TIMELINE!!! The one on the shadowland website is good, but it only covers Seattle or global events.

In case I didn't mention it, a complete timeline would be good...

'The Complete Collected Tables' would be ace. Just to stop you trawling through and damaging your other books while you do it looking for that one modifier.

And then the Holy Grail... a Complete Index with book and page references. Oh, just the thought of that and I think I need to go change my trousers...

Background, background, and more background. New Seattle if the game is going to take place in Seattle; if not, Corporate Download, Underworld Sourcebook and Shadows of North America. And maybe you should add the novel 2XS.

Snow Crash!

Cryptonomicon might be a pretty good choice, since it has some stuff set in the Philippines that can give you some idea of what the SR world could be like.