Good question! My first guess is that they'd fit somewhere in the spectrum of modern day crustaceans- somewhere along the shrimp-crab-lobster spectrum. Odds are, though, that most trilobites wouldn't be especially tasty- we definitely only eat some of the crab species out there for instance. Also, most trilobites were tiny, so there'd be essentially no meat on them.

That was all just my first thought, though. After a bit more thought, I recalled that they're more closely related to horseshoe crabs than proper crabs, and horseshoe crabs are essentially inedible, except for their roe, so there's a good chance they would have been inedible.