Where can I buy 4' x 10' sheets of red oak plywood around Minneapolis, MN?

Why are you using plywood and not just red oak? I think red oak would be stiffer than plywood. Are you talking about solid red oak plywood? I'm not sure that such a thing is made, is it? I assume it would be red oak laminate over softwood. Definitely could be wrong though.

I'm talking about plywood with red oak veneer.

Like http://www.homedepot.com/Lumber-Composites-Plywood-Sheathing-Subfloor-Plywood-Hardwood-Plywood/h_d1/N-5yc1vZbu0h/R-100046409/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053 but in 1/2"x4'x8' dimensions.

ok just wondering why you wouldn't use red oak? I think it will be much stiffer than plywood for a given thickness. At least I think so. Plus...any cuts you make from the inner sheet will have to be re-edged in red oak veneer. Which...isn't easy.

http://www.industriallumber.net/CATALOG/Hardwood%20Plywood/Oak.htm are local to minneapolis, but it appears 4x10 is only available in 3/4". As for the price on that 1/2", that's a pretty standard price I've seen everywhere.

I might not be understanding what you're intending here but in a case like this I'd probably just do a 1/2 inch edge on either end of the shelf. I'm thinking of something likehttp://www.familyhandyman.com/DIY-Projects/Woodworking/Woodworking-Tips/how-to-install-edging-for-plywood but on the sides as well. That would also allows you to customize in case the shelves near the bottom are 49" but at the top they're 48 1/2" (although perhaps your house is constructed to tighter tolerance than I'm used to.

You'd have to get really lucky to save any money this way. Try calling http://www.industriallumber.net/ but I suspect you'll find that the specialty product will end up costing more, not less.

Just looked through the online product listings for the distributor I linked above. They only offer 4 x 10 red oak in 3/4" thickness, but that's probably appropriate as noted above. You'd want to ask them about their products: # 25046, which is oak veneer on MDF, with nice veneer on one side and crappy veneer on the other side. # 25047, which is veneer core plywood with good veneers on both sides. #25048, which is veneer on MDF, with good veneers on both sides.

I would really do this out of regular red oak lumber and not plywood. With plywood, as others have said, you'll have to apply a veneer or facing to at east one edge. And even with a good finish-grade plywood, it's still just not as nice-looking as board lumber. I work at an office supply retailer, and we sell some very nice ($700+) veneer bookcases. I've never been terribly happy with veneer, especially for things like bookcases. If your bookcases are going to be mostly for show, that's one thing; if you're like me and are into your bookcases daily, the veneer starts to become a problem. All it takes is one accidental snag, or the veneer has just enough of a gap in the join to snag a shirt sleeve, and you wind up tearing a large piece of it off. And this is from a quality manufacturer. I've seen all too many DIY projects with applied veneers, and no offense, but the people just didn't know what they were doing. It takes practice to make a veneer look good. I'd bet that, all things considered, you'll be at about the same cost and certainly less time to just do it with good board lumber. You can easily put a slight bullnose on the edges to keep them smooth, and they'll be stiffer and look better than plywood. Plywood is great for covering large areas, but for 18" or 16" deep shelves, I'd really go with 3/4" lumber. A contractor I know likes to say, "Use good lumber for things you'll see, plywood for things you won't."