Here are some photos I uploaded for those interested in these three cases. I took photos of all three cases so you can get an idea of the thickness relative to one another.
I also included some thoughts, below.
Poetic KeyBook Removable Bluetooth Keyboard Case
I'm impressed by what you get for about $35. The N10 fits great and the keyboard is held in place with magnets so you can remove it; it'sthinner without the keyboard and actually resembles the i-Blason (below) without it. The keyboard has a decent feel to it, the keys are smaller than a standard keyboard. It pairs easily.
Poetic SLIMLINE Portfolio Case for Google Nexus 10
This is by far my favorite case. It's inexpensive, the "smart" cover works every time. It does not add bulk and it's well made. This will be my daily driver cover.
i-BLASON Google Nexus 10 inch Tablet Leather Case Cover with Stylus loop
This was the first case I could get my hands on. It's okay but overpriced by comparison. The "smart" functionality works about 10% of the time. It's bulky but it does protect and it's usable, just not for me.
Click here for all the photos.