People saying 200 books sounds excessive... if you get them cheap and keep them from cluttering up the place (could be true of anything, like toys)... You can fit 2-3 kids' books in a horizontal inch of shelving, so we're talking about, let's see... maybe 6 feet of shelf space? Two 3-foot shelves?
And I guess I don't see how, if space/money/organization aren't the issue, one can ever really have "too many" books. Maybe the wrong *kind* of books, if they aren't being utilized at all. But I don't see how one could say, "Well, 50 books is enough for a 4-year-old" or whatever. Sure, you can make do with any number, but I don't see where there should be a limit, per se. Seems really subjective.
I agree with this! We have easily triple this number (though granted 2 kids, not 1) and I'd say that decently organized, they would probably only take up a medium bookcase. As is, we have them divided between the living room and the kids rooms, and nowhere do these books occupy more than 2-3 "average" shelves. I don't really get the "clutter" issue.