Sielecki developed this repertoire working with students who were looking for something that was easy to understand and to learn. Most of the lines he selected are occasionally played by grandmasters, but on the whole they lie outside the mainstream of opening theory. That means that there is hardly any need to monitor theoretical developments.
Sielecki always clearly explains the plans and counterplans and keeps you focussed on what the position requires. Ambitious players rated 1500 or higher will get great value out of studying this extremely accessible book.
Christof Sielecki is an International Master from Germany. He has been teaching and training chess for many years, and runs an extremely popular YouTube channel called ChessExplained.