I use a
Fibrament stone and highly recommend it.
Cook's Illustrated's "top choice" is
King Arthur's baking stone but I do NOT recommend it for the following reasons: (both the Fibrament and KA were in CI's baking stone review)
Fibrament: 3/4" thick
KA: 1/2" thick
At the same size, the fibrament is much heavier and you'll want that in a baking stone so it retains more heat. For some reason CI cited the heavier weight as a "negative." Huh?
I found it questionable that they mentioned nothing about the importance of stone thickness and even thought of heavier weight as a negative.
CI also mentioned that the Fibrament had a cement-like odor every time they used it. If they actually read the manual, they'd know that they have to season the stone (progressively heat from 200 > 500 F over a few hours) first before using it. This eliminates factory odors and any excess moisture that might cause it to break.