Make sure you use a good outfitter for the drop. It is rare, but I hunted the south slope of the Books range one year and missed the migration. We were hiking in from the haul road, which had a five mile corridor for bow hunting only. We set up camp near the road and hiked five miles each morning to start our hunt. After a few days, we ran into a AK Fish and Game employee who told us the migration was two weeks late, so we might as well go home and return later. But a good outfitter will know where the herds are and can drop you near the migration routes. Good luck, dress for all weather and have fun.