Which books bridge the gap between Second Book of Go and Elementary Go Series?

Despite its name, Elementary Go Series is anything but elementary and is only recommended for players close to SDK.

I am around 16 kyu on OGS, having read A Complete Introduction to the Game and The Second Book of Go.

TPK tsumego (first two volumes of Black to Play! Train the Basics and first volume of Graded Go Problems for Beginners) are too easy; I get over 95% right within a few seconds.

For DDK tsumego (third volume of Black to Play! Train the Basics and second volume of Graded Go Problems for Beginners) I need to think for 15-60 seconds per problem and still get only about 75-80% correct.

What books would you recommend to reach the level where I can benefit from Elementary Go Series?