Soooooo, you're opinion iiiiiiiis?
If I only remember seeing three commercials for books out of the thousands of ads on TV I've seen since 1979, it's not worth the expense. One was for a paperback I bought based on the ad (don't even remember the author's name but it was for a third-rate thriller called
The Mime), one was for Stephen King's
Misery, and one was for a James Patterson novel that I don't even remember what it was called. Might have been for his current, might have been for one published six years ago.
Just remembered: also one for King's
Delores Clayborne. So, yeah. Four book commercials. Not very cost effective, even if it's for one of the Big Names. As mentioned above, if you want to advertise you'd better off leaving bookmarks on freebie tables at conferences or sending out postcards via direct marketing mailer.