Can you help me with these shelves?

First of all! No matter how a corner looks to the eye, they are not perfect. Lean the shelving unit in the corner you want to place it. Check to see if it fits against the wall corner. Use clear silicone caulk and place a bead of caulk on the back of each shelf. Then press the shelving unit in the corner making sure the caulk grabs the wall. Place/lean something heavy against the shelving unit to keep it against the wall allowing a few hours or overnight for the caulk to cure. In the future you can pull the shelving unit from the wall with minimal damage.

Try concealed floating support shelf brackets!

A couple of options:

Predrill holes in the spindles and screw to the wall. Counterskink the screws and fill the holes or paint over the screws so they aren't so noticeable.

Screw small boards that are painted to match the wall to the wall that several of the shelves rest on. I'd use lathe boards.

If the sides that go against the walls are flat, try using Command Strips. They are inexpensive, easy to use and won't damage your wall. I did use them to help anchor a shoe rack to my closet door and use them all the time for picture frames.

However you do it...........I would saw off the feet, otherwise it will always look like a floor shelf hanging on the wall.

My thoughts would be similar to a previous suggestion. I would use a larger size quarter round. One flat side to the wall the other to rest the shelf on and then screw through the shelves to keep them secure. To hide the brackets (quarter round) I would paint them the same color as the wall as suggested above.

I have seen these turned upside down and hung in a corner and they look good, and take less space from room.

After making sure the corner is square, level the shelves and make pencil marks. Also locate the vertical studs in the wall. Buy a pocket drill kit from any hardware store and drill two holes per side, matching the holes to align with the studs.

postion the shelves and screw cabinet screws through the shelves, into the studs. Use caulking to hide the joints around the wall.

you are done!!!

http://www.ebay.com/itm/12-pc-corner-brace-right-angle-bracket-plastic-clamp-shelf-support-/232110449769?hash=item360adc6469:g:ezYAAOSwZQRYYir3

This is the type of bracket I'm looking for. Since it's clear plastic it would be less likely to be seen. You really should use screws for sheetrock; they go in and then you turn the screw to make the attached piece open up to rest against backside of wall. Alternate if you can find a clear L bracket; rest the shelf on the foot of the L. Use a little paint same color as the shelf to cover head of nail or very short screw. If side of L is similar in height to thickness of shelf it might not be noticed and the sheetrock screw would be hidden by the shelf. Maybe 1/4" to 1/2" side and 1" bottom. The sizing difference of the shelves is what I can't quite get idea for mounting. Works no matter if you are just trying to keep in corner on floor or mounting farther up wall. If going up higher remove legs or maybe you could use them to attach a small plant pot under the shelves, using fishing line, Or maybe some beads.

There's really no safe way to do this without actually hooking it to the wall. Small "L"brackets [under the middle shelf] are your safest bet.

If you have a router and are not against cutting the wood of the shelf itself, you can get a keyhole bit to cut slots in the shelves. I would disassemble them, cut the backs that are going against the wall flat (you can get really fancy and use a scribe to make sure the contour of the shelf fits the wall exactly, but probably be okay with a bit of calking compound to fill small gaps.). I'm not a fan of the spindles, so I'd look for a way to repurpose them, and use plugs or buttons to fill the holes. Put appropriately sized screws into the wall (using molly bolt screws or wall anchors if you are going into sheetrock) at the levels you wish to hang each shelf, corresponding with the keyhole slots you cut. The shelves will appear to float on the wall. Use caution not to overload the shelves, because a keyhole slot that is too shallow can tear out. Do put the slot as deep into the wood as you can. I have a home-made shelf with keyhole slots that holds keys and light jackets and a few nick-nacks. If I remember, I'll post a photo. Google "using a keyhole bit" if you are not familiar with them. They really are a cool addition to your router tool. http://www.woodmagazine.com/woodworking-tips/techniques/routing/keyholes-bits