I know two people. The first knows Steven rather well and serves as a beta proofer for the manuscript. So when it comes back from final edit he gets a copy with permission to let a few people read it. Second person is one of the moderators of our reading group and she works for one of the world's largest book distributors and channels many of the review copies for national publications. Between them I get quite a few Advanced reading copies. And the reading group I belong to includes 7 published authors and about twice that in editors and such. All in all, I think the only books we don't see ARCs in are Rowlings and Jordan. Rowlings because they don't exist at this stage (though one member has a lovely and no doubt valuable galley of the first HP) and Jordan because whoever gets them first usually does not let go.HUH? You do mean the one by Steven Erikson, correct? That isn't even available on canadian booksellers! How?
One of the problems with reading galleys over ARCs is that there can be considerable changes to the material when it reaches final publication. Which I have found out to my extreme puzzlement when I read the next book and have no idea why something happened the way it did when the galley clearly had it happening another way. Or not happening at all. George R. R. Martin's second and third books had small but incredibly significant changes as I recall and I wasn't that thrilled with the original let alone having to go back and read it in final publication form to figure out what was going on.