It is a measure of one’s mental depravity that books about the Soviet Union are not merely interesting, they are enjoyable. Yes, I have enjoyed inhabiting Stalin’s Court, as described by Simon Sebag Montefiore, enjoyed Solzhenitsyn’s Gulag, enjoyed the ice-bound, despondent verses of Akhmatova. Owen Matthews taps into this strange phenomenon. Black Sun (Bantam Press, £16.99; Tablet price £15.29) is a superbly crafted thriller set in the hidden city of Arzamas-16, where, in 1961, a group of Soviet scientists are pioneering a nuclear bomb which will make Robert Oppenheimer’s horrific development of the same in 1945 seem like a child playing with a chemistry set. Matthews, who really knows the Soviet world, evokes it with absolute authenticity. A KGB officer, a “good” KGB officer, Major Alexander Vasin, is dispatched to this weird city to investigate the suspicious “suicide” of one of the key research scientists, just days before the new bomb is tested.