So... honest opinion?
Three 64 page books is better than one 256 page book. But only if handled right. And I don't think they're quite handling it right.
Break it down Core Books style. Player's Guide, Monster Book, DM's book.
Most of the setting and upward facing material goes into the Player's Guide which the DM reads, too.
DM's Book expands on what is in the Player's Guide, giving the deeper background of organizations and entities, setting threads, and mechanics.
Monster Book is just monster stats, locations, and lore.
Then, the DM can hand the players the Player's Guide before the campaign starts and let them read it cover to cover. There's nothing in that book that provides them too much information or whatever. It's -just- player-facing options and setting information that is common, or common enough, knowledge. No risk of them flipping to the DM portions of the book to learn more about background stuff or stat blocks for setting NPCs or Monsters because all of that is in another book.
Then make 64 page Adventures going forward... and you've got content and a half.
It's how I was looking at organizing Sins of the Scorpion Age for release. A Player's Guide with basic information about all the important cities and stuff in the world, then a Narrator's Guide with greater depth of each of those locations and DM-facing materials. Sold together at "Book Price" or you can buy the Player's Guide separately for a little less.
Because that's another thing... getting the Player's Guide to Spelljammer into players' hands separately and at a cheaper price point would be -huge-.