This one really needs no explanation. With printed books, sadly, going semi-obsolete, here's one thing you can do with them- make 'em into a kids playhouse or tiny (INDOOR) house! -Just make sure you have strong floor joists, as I can't imagine what this many books would weigh! I'd guess they're held together with drilled holes for rebar, or at least glued- if this were to collapse on a child, it just may ruin his/her, and YOUR, day.
-Derek "Deek" Diedricksen