Rutland Glass and Hearth Cleaner is great for removing smoke stains from both glass doors and masonry hearths.  Its nontoxic, easy to use and sold in 1 qt bottles.  $7.25

Speedy White Hearth and Stove Cleaner is a highly effective biodegradable cleaner. There's nothing better for removing smoke stains from glass doors and stone or brick hearths. 

For glass doors, simply spray on and wipe off. For stone and brick hearths, spray, brush, and sponge off. Aside from removing smoke and creosote, (Not recommended for brass, slate, or aluminum). 22oz. Spray bottle. $5.39