I've read some books published in the Soviet Union, by official publishers; obviously the ruling doctrine was Marxism-Leninism, but did this ideological requirement ruin any chance of objectivity for historians? Can they be relied upon on some level for non-Soviet readers?
As a side note I also find interesting that Soviet education actually taught Marxism, which would seem to possibly undermine Soviet rule. Was Marxism totally neutered in the Soviet Union?
'Ruin' may be a strong word for the most of the cases, but history was extremely important for propaganda, so yes, at least popular history teachings were highly influenced by ideology.
At the same time you have to understand that it was rare that someone lied about historical events. it was mostly about the interpretation of these events.
For example, you could read Soviet Historiography on Russia and the Mongols by C. Halperin (http://www.jstor.org/stable/129604). TL/DR: It was obvious for soviet historians that Mongol invasion was a catastrophe, "which the great Russian people manage... to overcome".
In some cases — mostly the history of Revolution and the history of the USSR itself — you have to be very careful about the facts also (or, their absence). It could be naive to expect from the Soviet historian to write in 1960-1970-1980 a honest and objective article about Stalin's purge.
Even now some topics are still hot and could be the subject of extensive public discussions. For example, the case of 28 Panfilov's Guardsmen. It was officially said that these soldiers destroyed 18 german tanks in one fight. All these soldiers were endowed with the title Hero of the Soviet Union posthumously. It was a very popular war story in the USSR. There were movies and books about these heroes, memorials for them and so on.
But it was proved in 1948 that this fight has never happened, and some of these soldiers were in fact very much alive. This research was top secret but in 1960-s it was proved once again. Now it was published in the 'New world' (Новый мир) magazine, and the result of this publication was very angry Leonid Brezhnev. So, official version of these events remained the same. It was debunked again and again in 1980-s and 1990-s, and it seemed that this is the end of the story, but in 2015 russian historian, head of the State Historical Archive, once again said that this story was a myth and immediately was heavily critiqued for this by the head of the Ministry of Culture (his boss).
So, the short answer is yes, soviet and russian historic research could be very useful and interesting, but you should read such research with the same attention and attitude as you'd read some text from the history. Some of these texts were influenced by the times when they're were written. There could be an agenda.