Agreed: Snow Crash is superb.
I'll second Neal Stephenson. Snow Crash is one of my favourites of all time. I will say I had no idea what I was getting into with Cryptonomicon, but I do not regret a moment of reading it.
My finished maps
"...sometimes the most efficient way to make something look drawn by hand is to simply draw it by hand..."
Robert L. Forward for hardcore science fiction. He did an excellent job of combining interesting science with interesting narratives and characters.
James Alan Gardner for more traditional science fiction. The second book in his League of Peoples series is a bit weak in my opinion, but even so it's my favorite science fiction series.
I don't know if either will cause you to run for a dictionary, but Forward's novels may cause you to flip through some science text books, and I greatly enjoyed the manner that Gardner put forward many of his "big ideas."
Alistair Reynolds - House of Suns - I can't recommend this one enough.
Dan Simmons - Illium duology & the Endymion & Hyperion books - massive, sprawling, full of dictionaria, though I prefer Illium.
Olaf Stapledon - Last and First Men - an epic, massive work, now almost forgotten.
Philip K. Dick - Valis - this one is whacked out, but Philip K. Dick is quite a classic.
John Scalzi - Old Man's War - an accessible but interesting series. Fuzzy Nation is also fun.
That's all from me for now .
How about Frederick Pohl's Gateway/Heechee series. There's also James Hogans Giantstar series, though that one isn't particularly "star spanning" in nature. Piers Anthony's Bio of a Space Tyrant, again, not "star spanning" but still a pretty good read. Recently I read Leviathan Wakes (James Corey), which wasn't too bad, and started reading Paul McAuley' Quiet War series, but I'm not too far along in that one, so can't say for certain how good it is just yet.
EDIT > Oh, joy, my evil 666th post here. Maybe I better stay in bed tomorrow.
When nothing is going right and you can't find someone else to blame, start beating your head against the wall, 'cause it'll feel so much better when you stop.
Peter F. Hamilton has written some pretty good sci-fi epics recently, and quite a few of them include some reasonably detailed worldbuilding. It would be fun to make maps of some of his worlds.
Most books won't have you reaching for a dictionary, unless you are new to the Engish language. Most writers are too obtuse to attempt stretching their vocabulary.
Check out Baen Books' catalog - they frequently have teaser chapters and indeed entire free books to sample. Travis Taylor does excellent science, and doesn't dumb down the vocabulary too much. I like Zahn's people and his gadgetry, and his plots work.