Today I would like to recommend the books written by the korean go institution
どんどん解いて強くなる 世界チャンピオンを育てた最強ドリル, Become stronger and stronger, books who made today’s world wide champions.
The books starts from the very beginning level up to the dan level. For each level there is a total of 4 books containing a wide range of problems such as (Tsumego, Tesuji, Fuseki, Ｊｏｕｓｅｋｉ…). The price is about 1500Yen in Japan.
I have been using these books for a year and am now a 1dan player even though there are some problems on the high ranked kyuu where I still make mistakes.