sogang books seemed pretty decent although this is the only one of the series that i have used. used it for an in-person korean class at uni, fairly slow pace good for beginners. definitely better to use with a teacher, but you could probably self study from it if you have someone to practice the speaking or correct your answers for you! getting the whole set of three is definitely a must. the workbook is helpful and the supplementary grammar/vocab book explains everything in detail which is necessary to understand the textbook. definitely a good option for those who want to focus on speaking more, but you’ll definitely want to learn some more vocab on the side in addition, trust me it’ll help a ton! (unsure about the price in comparison to other textbooks but at my uni it was 35usd for the workbook and 66usd for the textbook and supplementary book) in comparison to the integrated korean series this is much slower paced however slightly easier to self study from and involves more speaking in the curriculum