I was referred to this Series when browsing a list of best British spy series, realising that I have seen a little with David Tennant (whom I like) present and all this has been him being a policeman/detective... So I decided to kill two birds with one stone and delved into the world of frivolous glamour, deception and betrayal in a period when particularly smaller nations in Europe had uncertainty and difficulties in many layers.
Well, the events got going, the depiction seems realistic (several episodes based on real events), the cast includes pleasant British character actors (Tennant, Lesser, Haddington) and some also good Polish actors -- so I really can´t say that Spies of Warsaw is protracted or dull. True, I had-have not read the book, but in thrillers, for the sake of delight, I prefer twists and solutions unknown beforehand - it is yet no Hamlet or similar, after all...
Additional plus for the depiction of an era rather unknown today - Poland in the late 1930ies, and with both Warsaw and Berlin being splendid cities with fine architecture destroyed by subsequent war.