Cheap stocks can get cheaper. They often do. Unfortunately, "cheap" is a relative term. Precious few stocks that trade for low price-to-earnings ratios or below book value are real bargains. They look enticing, but they're actually value traps -- stocks that deserve the multiples for which they trade, and punish the trashpickers who buy them.
Book value is shorthand for equity. A low price-to-book stock is priced as if management won't produce high returns from the equity capital afforded it.

Keep a distance from SYMM and watch it closely. Burning rate is high.