I am going to Istanbul for four days. What map would you recommend I buy?
I recommend Rick's Istanbul guidebook, which includes probably all of the maps you need, or a Lonely Planet book will also have enough to get you to your hotel. Supplement that with a free map from the TI desk in the International arrivals area of the airport and Google maps that you access online (e.g., while planning at your hotel).
Insight Fleximap, since Streetwise doesn't have one for Istanbul.
I didn't find the maps from the RS book to be helpful, except for the self-guided walking tours. My first hotel had a very good free map. Every time I asked how to get somewhere, they used a new one to show me. My second hotel only had a very useless free map.
Mr Steves does many things extremely well.
Being a cartographer / geographer is not among them.
His maps, like the text, only show what he considers important.
An analogy would be my drawing a map of Florida that showed only my house, two alligators, a hardware store, a grocery store, and seventeen bars.
Thankfully, no one cares where you dwell Ed.
if you're generally ok with direction it's pretty easy to navigate Ist. on the old town side use the metro line as reference, and if you cross the bridge go left up the hill you get to tuksim square, go right along the water is dolmabahce palace. if you have time you can walk to everywhere, but dolmabache is a little out of the way and you can't really walk along the water. with that if you use the free map from hotel you should be just fine.