This mosque is grand and is impressive inside and out. The Hagia Sophia is nearby and is a very interesting building but the Blue Mosque was constructed as a mosque and you can tell a lot of time and effort went into its design and construction.
Entrance is currently free for all people but you have to be respectful of their rules. Entrance to worshippers is on the north side and non-worshippers must go to the south side. You must dress conservatively here so pants, shoulders covered and a head scarf for women. There is a couple of bottle necks to enter the mosque for non-worshippers including a queue and a small doorway where you have to remove your shoes. There are staff that will check to make sure you remove your shoes and inspect women for head coverings. It is important to note that they will close during prayer time and the biggest closure is during the Friday prayer.
Once inside there are plenty of shelves to put your shoes and you can stay as long as you like to appreciate the interior. There are free information centres inside the mosque that explain the religion as well as an exhibition in the courtyard that explains the history of Islam and Muslim contributions to the world. We got some really good pictures of the mosque from the inner courtyard. It is a tourist hotspot but I was sad to see large tour groups going in and guides blocking certain areas instead of just allowing people to enjoy the visit.
There are a ton of attractions in the area including monuments from Roman times and museums with artifacts from all eras of Istanbul and Constantinople. The area is very walkable and there are a lot of shops and restaurants nearby. It gets very busy midday so it is best to get there early for the best experience and if you want to avoid the crowds. There are trams and busses that frequent the area.
I found myself in the area a few times during my visit to Istanbul and felt seeing the Blue Mosque at night was also worth seeing if you're in the area. I found the pictures I took did not do it justice and it looked much nicer in person.