Skip Codex by Lev Grossman. It was another silly vacation read maybe a fortnight ago.
Young investment banker looks for ancient book, assisted by slightly frantic graduate student, both of them caught up in some odd royal family power struggle. Even for a “beach read,” pretty dismal. I read it, so you don’t have to. It was sitting on a shelf, and the jacket promised another historical manuscript mystery, of a sort, and I’m clearly a sucker for those right about now.
By the way, I almost always finish the books I start, even if they are not worth the hours. Probably not the only place I waste valuable time, but one habit ingrained in my soul. I know others who find it hard to finish books they start, and I alternately envy and pity their different style.