Tarkovsky was a very serious person. His films are some of the greatest I've ever seen. I saw all of those at least 20 years ago. I hope this Dyer is not using, i.e. exploiting, Tarkovsky for his own ends, as the whole of Tarkovsky's oeuvre should be examined as a whole. I fear that Dyer's book is based on a number of other works about Tarkovsky, as several have now appeared since his death including, recently one by his last interpreter between Russian and Swedish, Laila Alexander-Garrett.
There seems to be no reason to pull out "Stalker" on its own. His other films, such as "Andrei Rublyov", "The Mirror" and "Solaris" also show aspects of Russia that were rarely tackled at a time when Russia was the leading state of the Soviet Union. And Tarkovsky proved to be the exception to the rule of conformist and heavily politicised Russian film-making. The Russian establishment no doubt allowed him his freedoms because they realised that he was good propaganda abroad, showing that the Russians did not entirely follow their own canon of socialist realism. But in the end, Tarkovsky was obliged to make films abroad (Sweden, Italy) and these are not as convincing as the ones he made back home in Russia.
"Stalker" was, incidentally, filmed in the port area of Tallinn, in what was then the Estonian Soviet Socialist Republic, and the first book about Tarkovsky's work published in the Soviet Union was by the Estonian-Russian Tatyana Elmanovich ("Ajapeegel" [Mirror of Time]; 1980). This is a serious book, where Elmanovich examines four early Tarkovsky films, including "Stalker". Tarkovsky also used a couple Baltic actors (one Estonian, the other Lithuanian) for a couple of his key films. And his last film was filmed on the island of Fårö, off Gotland, Sweden, because by that time Ingmar Bergman had lent him his film crew.
Another book worth reading (this time available in English) is "Sculpting in Time" (1986) which is Tarkovsky's own reflections on the cinema and his own work. His father Arseni Tarkovsky's poetry is heard recited in the film "The Mirror" if I remember rightly, but I'm not sure how much of this poetry has ever appeared in a good English translation. Arseni T was also a prodigious translator from various Soviet languages and Polish.
So given what I've read in Leyla's review and on the net, I'm pretty sceptical about how seriously Dyer is examining Tarkovsky as a film director, rather than just pulling out one film that he's seen again and again, and embroidering upon it, adding anecdotes about himself.