I sent an email to the kind people over at the bookstore and she sent me great directions! We started at Taksim Square, took a bus to Besiktas, and from there walked over to board the ferry to Kadikoy. After a 20 minute ride you land at this station. This is the front of that building. With your back to this building walk to the crosswalk.
When you are standing at the crosswalk you will see this building directly across the street. Walk to that building and take the sidewalk to the left (just follow the crowd!)
You will see this Starbucks after you follow that pathway to the next street over... cross to where the Starbucks is and walk to the right of it. Follow that walking street up one 'block'.
When you reach the intersection you will see this church. Turn right at that street. The street name is Murhurdar Caddesi but knowing that didn't help as there was no street sign there... just turn right at the church!
Walk up that street until you get to Burger King and turn left.
And although this photo is shot from other angle you will see the bookstore on the right side of the street about 8 doors up from Burger King!
Enjoy your time there and trust me it will be worth the effort!!
A write up of the bookstore is located here... It is on the Asian side of Istanbul, and they have the largest selection of books English that we have seen so far. The bonus for us was the wide variety of Christian books. After spending 5 years shopping at a Christian bookstore in Krasnodar with only Russian books to offer this was a real treat to our souls!