Korean study books, which would you advise?

[Dudie]

I recently picked up my Korean studies again which I'm learning by myself. I do listen/read TTMIK lessons every day and I do have a "Hello Korean" book, but I don't find that book handy because I have to go back and forth all the time since the translations are in the back. I'm looking for other books which are easier to use and there are so many. I have been thinking about buying the TTMIK books or the ones by Sogang University. But I also saw Yonsei, SNU and Ewha has study books and many other options. 
I heard good things about the Sogang books but I haven't read a lot about the others, anyone uses those and can tell me about them? And most come with a text and workbook, is a workbook a must when you study by yourself or only when you take classes somewhere?

[Guest hakyeon1e]

This book helped me write, read, and speak Korean on a standard levelI hope it helps you.

[Dudie]

Thank you I don't know that book yet but I will look for some reviews online