Two initial sets of puzzles straddle a chapter entitled "Find the Wrong Move" in which each diagram precedes a catastrophic blunder perpetrated by a strong player, which the reader has to identify in advance. The fourth chapter too is innovative: a selection from the great tournament at Karlsbad 1911, set in the context of how their play compares to today's players.
For all the 202 positions in these four chapters, Nunn provides hints in a separate section. Naturally, though, this facility is not available for the final section of eight self-assessment tests of six positions each for a grand total of 250 puzzles in the 208 pages.
While the organisation is most interesting, it is the level of difficulty that marks Nunn's book out. In the introduction he explains that he's "rated the positions on a scale from from 1 to 5... Only those rated 1 and 2 are suitable to solve on a train: the rest should be set up on a board". This is tremendous stuff, particularly for the ambitious club or stronger player who is prepared to devote sufficient time to it, but not for the faint-hearted.
Here is a nice example of Nunn's level 2:
Black to move
In Spirov vs Najdorf Lodz, 1932, Black won with 1 ...Qc6!! when:
a) if 2 Bxc6 Bxc6+ 3 Kg1 Rd1+! 4 Qxd1 e2+ and mates.
b) White tried 2 Ba3, resigning after Rd2 3 Bxc6 Bxc6+ 4 Kg1 Rxe2 5 bxc5 Rg2+ 6 Kf1 e2+.