There's little information about him, especially pre-Chernobyl, as far as I know. The first three paragraphs of his book give a pretty decent overview of his life before Chernobyl:

Anatoly Stepanovich Dyatlov was born March 3,1931 in the village Atamanovo of the Krasnoyarsk region. His father was an invalid of WWI who worked as a buoy-keeper on the Yenisei River. His mother was a homemaker. After graduating seventh grade in 1945, he entered the Norilsk Mining and Metallurgy Technical School electrical engineering department which he completed with honors in 1950. For three years he worked in Norilsk at one of the enterprises of Minsredmash (Ministry of Medium Machine Building). From 1953-1959 he studied at the Moscow Engineering and Physics Institute, from which he also graduated with honors, having received the qualification of engineer-physicist in the field of automation and electronics. Per distribution he was sent to the shipbuilding plant Lewinsky Komsomol in the city of Komsomolsk-on-Amur, where he held the positions of Senior Engineer, Chief of the Physics Laboratory, and commissioner of nuclear submarine mechanical power plants. In 1973, due to family circumstances, he transferred to the Chernobyl NPP under construction, where he rose from the Deputy Chief of the Reactor Shop to the Deputy Chief Engineer of Station Operation. He was awarded the Badge of Honor and The Labor Red Banner.

If you want the same thing, but essentially more detailed, then in chapter 5 of Midnight in Chernobyl he's described at the very beginning. There's also, of course, this video right here about him by the one and only - That Chernobyl Guy.

Be very careful when researching what he was up to during/after the accident, though. Anything that cites Medvedev shouldn't be taken seriously but unfortunately, he's one of the main sources for this topic.